U.o.     ->'^f'- 


^^       l^    '^//    ^^^^^.^^^Ay     /S.^ 


WAR  DEPARTMENT    -    -    OFFICE  OF    IHE  CHIEF  SIGNAL  OFFICER 


MANUAL  NO.  3 


TECHNICAL  EQUIPMENT  OF 
THE  SIGNAL  CORPS 


1916 


WASHINGTON 
GOVERNMENT  PRINTING  OFFICE 

1917 


\\'ar  Department, 
Dncuineni  No.  541. 
fice  of  the  ( 'hirf  Sigval  Officer, 


IL^,-^-. 


TABLE  OF  CONTENTS. 

('HAI'TKIi     1. 

The  voltaic  cell,  Ohm's  law,  aiul  primary  aiul  .^('((iiiilary  batteries 1 

C' HAI'TKII    2. 

Telegraphy  and  the  in<lui1ion  t olograph  wt 33 

CuArTKR  :'>. 

Telejihony,  (he  camp  lelephoiic  ami  t  he  Inizzor 67 

Chapter  i. 
Cable  and  (^11)10  sy.slems iOl 

Chapter  5. 
Aerial  line  construction 175 

Chapter  (i. 
Post  telei)h()nc  systems 211 

Chapter  7, 
Small-arms  target  range  signaling  systems 265 

Chapter  8. 
Technical  ecpiipment  issued  by  the  Signal  Corps 283 

Chapter  9. 
Miscellaneous  tests  and  general  information 381 

Chapter  10. 
Requisitions  and  general  main1enan<e  regulations 423 

Chapter  II. 
Long  submarine  cables;  Submarine  tclesraph\  ;  Tests  ol  longsul>marine  cables.       437 

HI 


.'J615^.7' 


INTRODUCTORY. 


This  mannnl,  whioli  siiporsodes  Mannnl  No.  o.  edition  of  1910,  and  Manual 
No.  4,  Handbook  of  Suhniai-iiie  Cables  of  tlie  United  States  Signal  Corps, 
1905,  relates  principally  to  the  latest  technical  equipment  of  the  Signal  Corps 
issued  for  held  use  of  the  mobile  army,  and  to  the  technical  eiiuipnient  in- 
stalled at  mobile  army  posts.  An  enumeration  of  all  Signal  Corps  equipment 
appears  in  chapter  S. 

Fire-control  systems  and  their  eiiuipment  are  described  in  Signal  Corps 
Manual  Xo.  8,  latest  edition. 

Technical  information  relative  to  radiofelegraphy  and  e([uipment  Is  em- 
bodied in  ••  Kadiotelegraphy  ■'( Signal  Office  Circular  Xo.  1). 

Information  concerinng  signaling  eciuipment  may  be  found  in  Signal  Book, 
I'nited  States  Army. 

Signal  Corps  Manual  No.  4,  Handiwiok  of  Submariiie  Cables  of  the  United 
States  Signal  Corps,  1905  has  become  obsolcir  and  information  relative  to 
laying,  operation,  and  maintenance  of  long  sulmiarine  cables  is  supplied  in 
chapter  11  of  this  manual. 


CnAI'TKK    1, 

THE  VOLTAIC  CELL.  OHM'S  LAW.  AND  PRIMARY  AND  SECONDARY 

BATTERIES. 

I'HK    \(>I.1'AH      (  Kl.l.. 

If  zinc  and  carbon  are  immersed  in  an  acid  or  .saline  solution  and  the  two 
connected  externally  by  a  wire,  an  electric  current  will  flow  from  one  to  the 
other.  Any  two  dissinnlar  metals  when  inunersed  in  an  ackl  solution  which 
acts  on  one  more  than  on  the  other  and  connected  externally  by  a  wire  will 
produce  similar  results.  There  are  a  few  nunmetallic  substances  which  if  used 
in  a  voltaic  cell  in  the  place  ()f  metal  elements  will  produce  the  same  result, 
'riir  sulimerijed  substances  are  termed  plates  or  elements,  and  the  solution  is 
termed  electrolyte.  The  combination  of  plates  or  elements,  electrolyte,  and 
containing  ves.sel  constitutes  a  voltaic  cell. 

Authorities  differ  as  to  .lust  why  a  current  of  electricity  flows  under  the 
conditions  stated  above.  Suflice  it  to  say  that  it  does  flow,  and  that  invariably 
one  (if  the  plates  is  acted  upon  (decompo.sed  or  eaten  away)  to  a  very  much 
greater  tlegree  than  the  other.  Experiment  has  shown  that  substances  uniler 
above  conditions  which  are  acted  uiion  eiiually  do  not  cause  a  current  of  elec- 
tricity to  flow.  • 

Where  carbon  and  zinc  are  used  as  the  plates  in  the  voltaic  cell,  the  carbon 
is  termed  the  negative  plate  or  element  and  the  zinc  is  termed  the  positive  plate 
or  element.     The  carbon  or  negative  element  forms  the  positive  pole  of  the  bat- 


Fig.  1-1.— VOLTAIC    CELL. 

.  tery.  and  the  zinc  or  posiUvc  clemeni  foinis  the  negative  pole.  The  reason  for 
this  apparent  ctmtradiction  is  as  follows  :  In  any  source  of  electricity  the  current 
flows  from  positive  to  negative,  and  in  the  voltaic  cell,  with  plates  connected 
externally  with  a  wire,  the  current  flows  from  zinc  through  electrolyte  to  car- 
bon;  this  is  termed  the  internal  circuit.     Outside  the  battery  current  flows  from 

(1) 


2  Signal  Corps  Manual  No.  3. — Chapter  I. 

carbon  plate  through  wire  to  zinc ;  this  is  termed  the  external  circuit.  Thus  it 
will  be  noted  that  in  the  internal  circuit  the  current  tlows  to  and  from  directly 
opposite  plates  to  those  in  the  external  circuit.  Figure  1-1  illustrates  the  above. 
The  term  "  circuit "  is  applied  to  the  entire  path  through  which  the  current 
of  electricity  flows.  The  wire  joining  the  plates  is  a  conductor.  Bringing  the 
ends  of  the  conductor  into  contact  is  called  making  or  closing  the  circuit,  and 
their  .separation,  opening  or  breaking  the  circuit.  A  substance  through  which 
the  current  readily  flows  is  a  good  conductor.  Any  substance  which  offers  an 
extremely  high  resistance  to  the  flow  of  an  electric  ciu'rent  is  an  insulator. 
Most  metals  are  good  conductors,  while  mica,  glass,  porcelain,  dry  wood,  dry 
atmosphere,  rubber,  etc.,  are  insulators. 

ohm's  law. 

With  any  circiiit  through  which  a  direct  current  of  electricity  is  flowing  there 
are  the  three  governing  factors,  which  are  as  follows : 

(1)  The  difference  of  potential  between  the  positive  and  negative  pole  of  the 
generating  medium,  known  as  the  pressure  or  electromotive  force,  the  Tinit  of 
which  is  the  volt.  (Abbreviated  V.,  E.,  or  E.  M.  F.)  One  volt  is  that  electro- 
motive force  which  would  maintain  in  a  circuit  having  1  ohm  resistance  a  cur- 
rent strength  of  1  ampere. 

(2)  The  resistance  or  opposition  by  the  conductor  to  the  flow  of  current,  the 
unit  of  which  is  the  ohm.  (Abbreviated  R.)  One  ohm  is  that  i-esistance  in  a 
circuit  which  if  impressed  with  an  electromotive  force  of  1  volt  allows  a  current 
strength  of  1  ampere  to  flow  through  the  circuit.  One  ohm  is  the  resistance  of 
a  column  of  mercury  about  42  inches  high  and  0.00155  square  inch  in  cross- 
sectional  area  at  zero  centigrade. 

(3)  The  current  strength  or  rate  of  flow,  the  unit  of  which  is  the  ampere. 
(Abbreviated  I.)  One  ampere  is  that  strength  of  current  which  would  be  main- 
tained in  a  circuit  having  1  ohm  resistance  if  imjiressed  with  an  electromotive 
force  of  1  volt. 

From  the  above  it  will  be  noted  that  a  deflnite  relation  exists  between  these 
factors,  so  that  the  value  of  any  one  of  them  can  be  found  if  the  values  of  the 
other  two  are  known.     This  relation,  expressed  by  Ohm's  law,  is  as  follows : 

(a)  The  current  strength  in  a  circuit  may  bt"  lound  by  dividing  the  pressure, 
or  electromotive  force,  applied  to  it  by  the  resistance. 

r,-  „N     E  M  F  (in  volts) 

/(m  amperes)—  ' 


R  (in  ohms) 

{}))  The  electromotive  force,  or  i)ressure,  i-eriuired  to  lUiiinlMin  a  certain  cur- 
rent strength  in  a  circuit  may  be  found  by  nuilfiplying  the  current  in  amperes 
by  the  resistance  in  ohms. 

(c)  The  resistance  in  any  circuit  may  be  found  by  dividing  the  electromotive 
ff)rce  by  the  current  strength. 

i>  /•      I  ™  \     E  M  F  (in  volts\ 
It  (ni  ohmH)  =  -  ,-,.  - —      -     v). 
/  (in  amperes) 

Wlien  the  total  electromotive  force  is  used  in  Ohm's  law,  the  total  rpsistance  musi 
be  used  to  calculate  the  current  strength.  For  example,  if  a  coil  of  0.5  ohm  resist- 
ance is  connected  to  a  cell  of  2  volta  E.  M.  F.,  the  current  through  the  coil  would  not 

V  2 

be  ^  or       =4  amperes  as  might  be  supposed.     It  requires  a  certain  part  of  the 

(2) 


Voltaic  Cell,  Ohm's  Law,  Batteries — Chapter   1 .  3 

cell's  E.  M.  F.  to  force  the  current  through  the  internal  circuit;  therefore,  the  inter- 
nal and  external  resistances  must  always  be  added  together  and  divided  into  the 
total  E.M.F.  to  find  the  current  flowing.  Now,  if  the  internal  resistance  of  the 
above  cell  were  0.5  ohm,   the  total  resistance  would    be  0.5+0. 5=^1  ohm  and 

F    2 
/=— =— =2  amperes,  or  half  of  the  first  result. 
K     1 

Ohm's  law  applies  also  to  any  part  of  a  circuit  the  same  as  to  the  whole 
circuit.  "When  applied  to  part  of  a  circuit  care  must  be  taken  to  use  only  the 
E.  M.  F.,  resistance,  and  current  strength  of  that  portion  of  a  circuit  considered. 
Therefore,  when  E  is  used  as  total  E.  M.  F..  R  nuist  be  the  total  resistance,  and 
when  E  is  used  as  the  pressure  applied  to  part  of  a  circuit,  R  to  correspond 
must  be  the  resistance  of  that  part  of  the  circuit  to  which  the  E  was  applied. 
This  api)lication  of  the  law  may  be  illustrated  by  the  followins  problem  : 

The  E.  M.  F.  of  a  cell  is  2  volts;  its  internal  resistance  0.5  ohm.  It  is  con- 
nected to  three  .si)ools  of  wire  in  series.  By  measurement  we  find  that  the  E 
causing  the  current  to  flow  through  one  of  the  spools,  of  which  the  7^=0.4  ohm, 
is  0.(5  volt.    What  current  is  flowing  through  this  spool? 

Bv  Ohm's  law  /  =^=-^  =  1.5  amperes. 
h     0.4 

Now,  since  the  current  is  the  same  in  all  parts  of  a  series  circuit,  1.5  amperes 
flow  through  each  of  the  spools  and  also  through  the  internal  resistance.  This 
also  illustrates  the  difference  between  the  E.  M.  F.  and  potential  ditference.  The 
difference  of  potential  or  pressure  between  the  ends  of  the  spool  is  0.6  volt,  while 
the  E.  M.  F.  of  the  cell  is  2  volts. 

What  part  of  the  total  E.  M.  F.  is  used  in  overcoming  the  internal  resistance 
of  the  cell  in  the  above  problem? 

By  Ohm's  law  E'^/X  7^=1.5  X 0.5=0.75  volt. 

This  gives  pressure  lost  or  "  volts  drop  "  inside  the  cell. 

The  resistance  of  any  conductor  increases  with  its  length  and  decreases  with 
area  of  cross  section  and  for  most  conductors  the  resistance  increases  with  rise 
of  temperature. 

Electric  ciu'rent  so  far  discussed  in  this  maniial  has  been  direct  or  unidirec- 
tional as  appertaining  to  its  flow  in  a  circuit  and  is  termed  "  direct  current." 
(Abbreviated  D.  C.)  This  current  may  be  so  treatiMl  that  it  will  become  either 
alternating  or  pulsating  in  character.  When* this  occurs  Ohm's  law  still  applies, 
but  there  are  other  factors  that  mu.st  be  considered  in  coniiniting  values  of  1.. 
E.  M.  F.,  or  R. 

With  an  alternating  current  (abbreviated  A.  C.)  the  flow  In  a  circuit  is  con- 
tinually reversing  in  direction.  Certain  types  of  generators  produce  alternating 
currents  which  change  direction  periodically  and  uniformly,  the  speed  of  rota- 
tion of  the  rotor  of  such  generators  being  constant.  Such  currents  are  expressed 
in  number  of  cycles  per  second,  60  cycles  being  the  most  conunoidy  used  for 
commercial  electric  lifihting  and  power  systems.  Two  alternations  (chanjre  of 
direction)  are  contained  in  a  cycle. 

Unlike  this  current,  the  alternating  current  produced  in  telephonic  comnni- 
nication  is  not  periodically  \nuform  nor  is  the  E.  M.  F.  in  any  way  constant. 
The  E.  M.  F.  of  these  alternating  currents  is  usually  extremely  high  and  the 
current  sti'ength  very  low,  consequently  the  source  of  the  current  for  trans- 
mitting the  voice  waves  from  a  single  instrument  need  only  be  capable  of 
producing  a  comparatively  weak  current  strength.     For  this  reason  a  person 

(3) 


4  Signal  Corps  Manual  No.  3. — Chapter   1 . 

ciiiuiii^'  into  c<ml:icl  willi  lioth  sitlt's  of  a  talkiiifj;  circuit  will  not  l)c  injured  iiy 
tlie  talkinjr  current. 

A  pulsating  current  is  one  whicii  varies  in  niaj;nitu(le.  As  ordinarily  em- 
ployed the  term  refers  to  unidirectional  current.  A  i)ulsatiug  current  may  als(j 
he  formed  by  superimposing  upon  a  direct  current  an  alternating  current. 
A\'hen  the  altern^iting  current  is  flowing  in  the  same  direction  as  the  direct 
current  the  former  accentuates  tlie  latter,  and  when  llowing  in  the  reverse  di- 
rection it  counteracts,  in  a  degree,  the  direct  current. 

These  curreiits  will  he  (>ncountered  in  the  study  of  the  ojiei-ation  of  the 
telephone  and  similar  appai'atus.  In  (liai)ter  1^  of  (his  manual  exjjlanation  is 
made  of  how  they  are  jn'oduced. 

Standard  P>a  itkkiks  Stpplied  hy  the  Signal  Corps. 

There  are  two  classes  of  hatleries,  viz.  primary  and  secondary,  the  latter 
being  sometimes  known  as  storage  batteries  or  accunudatoi's. 

Primary  batteries  are  divided  into  two  classes,  known  as  oi)en-circuit  and 
closed-circuit,  and  while  there  is  a  great  variety  of  each  class,  the  basic  ]»riii- 
ciple  employed  is  the  same. 

( >pen-circuit  cells  are  used  f<_)r  intermittent  service  where  curr»Mit  is  required 
for  only  short  intervals  of  time,  such  as  in  operating  electic  bells.  Open- 
circuit  cells  kept  in  continuotis  .service  foi'  some  time  become  polarized  or 
completely  exhausted  but  will  recuperate  to  a  considerable  degree  on  open 
circuit. 

The  dry  battery  is  an  excellent  example  of  the  oiien-circuit  type. 

Closed-circuit  cells  are.  adapted  for  sttpplying  current  continuously  until  the 
energy  of  the  chemical  is  nearly  (>xpiMuled. 

This  is  the  form  of  jirimary  cell  most  extensively  used  in  telegraithy.  where 
a  small  but  constant  cun-ent  is  re(|uired. 

While  f(»rmerly  tlie  Signal  Cor]»s  issued  several  difft'i'ent  kinds  of  oi)en- 
circuit  itriniary  battery  cells,  such  as  the  Laclanclu'.  (Jonda,  and  the  Sampson, 
all  of  which  employed  carbon  and  zinc  foi-  elements,  salanuuoniac  dissolved  in 
water  as  electrolyte  and  a  conlaining  Jar  of  glass.  t'xi>erience  has  shown  that 
the  di-y-cell  tyi)e  of  jirimary  battery  is  most  satisfactory,  and  consequently 
this  tyi>e  foiMus  the  standard  issue  of  the  Signal  Cori)s. 

While  all  dry  cells  ol'  this  ty|ie  conform  in  general  with  the  following 
(le.sci'iption.  it  is  found  that  different  makes  \ai'y  in  efliciency.  In  order  to 
ascertain  the  comparative  merits  of  each  make,  a  careful  life  lest  is  jyeriodically 
made  in  the  Signal  Corps  laboratory,  Washington.  1  >.  C. 

The  dry  battery  is  a  form  of  sal-ammoniac  batter\  in  which  the  zinc  plate 
consiiUHes  i)oth  the  containing  vessel  and  negative  |i<ile,  1  hei'eby  doing  away 
with  the  breakable  gla.ss  Jar.  An  absoi'beiit  porous  material  with  a  dei>olarizing 
mixtui'e  .around  it  tills  the  space  between  the  carbon  in  the  center  and  tlie  zinc 
vessel.  This  porous  materi.-il  is  salui-alc(|  wiih  a  solution  contaiinng  chloride 
of  zinc  and  sal  anmioiiiac.  The  top  of  liie  cell  is  seaJed  with  asi)halt  (»r  similai" 
material.  I'.inding  p(»sts  for  zinc  and  carlion  elements,  and  pasteboard  cover 
t(»  jirevent  sliort  cii-culliiiLr  wilh  adjacent  cells,  complete  this  form  of  battery. 
These  cells  when  carefull.\  manufactured  and  properly  stored  are  reliable. 
The  cell  can  not  be  i-enewed,  hut  their  low  cost  and  the  conveni(>nce  affcu'ded 
by  iialui'e  of  the  conslruciioii  makes  them  superior  jo  the  wet  cell  for  general 
use.  When  these  cells  are  exhausted,  a  short  jieriod  of  usefulness  may  be 
obtained  from  llieni  in  the  I'ollowiiiL:  manner:   ranch  a  number  of  holes  through 

it) 


Voltaic  Cell,  Ohm's  Law,  Batteries — Chapter    1.  5 

tilt'  zinc  (•ontaiiiiii^^  case  and  |ila<t'  (licni  in  Jars  containing'  a  solution  of  sal 
annnoniac  and  water.  Sal(  solid  ion  lor-  lids  imrposc  may  he  used  Inil  it  is  not 
as  elToctivc  as  tlio  sal  ammoniac. 

The  standard  sizes  of  the  dry  cell  are  shown  in  lijiure  1-2,  hut  it  is  pointed 
out  that  only  two  of  the.se  sjzes  are  in  ;4eiieral  use  with  jiost  teleithoue  systems 
and  Willi  insrrunients  use<l  hi  ti»e  field. 


-   v- 6i 


OCZJ 


TUNGSTEIN,  TYPE  A 


Dimensions  are  for  a^/ls  a/.'-j 
:Yiper  cov?rinq  rprnov?ct. 


No,4-0 


HL 


No.  8  No. 6  No.4 

Fig.  1-2.— BATTERY,    DRY    CELLS,    STANDARD    SIZES. 

Size  iS'o.  G.  lijrure  \-l.  is  invariahly  useil  when  a  local  hallery  is  desired  for 
telephones  of  post  teli'phone  .systems. 

The  tiintrsten  tyju'  A  hattery  shown  in  tijiure  l-'J  is  used  with  the  service 
huzzer.  the  1!)14  induction  tele.irraph  set.  the  camp  telephone,  radio  test  huzzer, 
and  the  hand  tlasldijiht.  This  type  of  hattery  is  similar  in  construction  to  that 
described  above  hut  in  order  tt)  obtain  a  comparatively  hifrh  volrase  with  mini- 
mum wei.fflit  and  bulk,  the  cells  ;ire  of  small  diameter  and  two  cells  are  so 
placed  in  a  rii;id  i)ai>er  tube  that  they  are  connected  in  series.  This  combina- 
tion uives  a  total  voltaiic  of  o — 1  ■]  beiiii:  normal  voltasre  of  eai'li  cell. 

RESKRVK  TYCK  DIJY   CELT.. 

The  ordinary  tyiie  of  dry  cell  deteriorates  if  kept  lon.ir  in  storasre,  even  thouirh 
not  in  nse.     To  jirovide  a  type  of  dry  cell  which  could  be  kept   in  sioraire  with- 


(5) 


6 


Signal  Corps  Manual  No.  3. — Chapter  1. 


out  deterioration,  tlie  Signal  Corps  issues  a  dry  cell  known  as  ttie  "  reserve 
type."  sliown  in  figure  1-3.  Tliis  cell,  although  containing  all  the  elements  and 
ingredients  of  an  ordinary  dry  cell,  does  not  become  active  until  water  has  been 
poured  into  a  cavity  of  the  carbon  element.  To  place  the  cell  in  service,  remove 
the  plug  from  the  top  of  the  carbon  element  and  fill  with  water  (rain  water 
preferred).  As  soon  as  this  is  absorbed,  fill  again,  until  the  following  amounts 
of  water  have  been  added:  Type  4-0,  li  ounces;  type  5,  2i  ounces;  type  0. 
3i  ounces ;  after  which  no  more  water  should  be  added  to  these  dry  batteries. 

Great  care  should  be  exercised  in  pouring  the  water,  in  order  to  avoid  wetting 
the  cardl)oard  cover.  If  no  funnel  is  availalile  it  is  advisable  to  remove  card- 
l)oar(l  container  during  tilling.  When  tlie  cell  becomes  wealc  through  \ise,  a 
little  sal-anniioniae  solution  placed  inside  the  cai-l)on  element  will  rejuvenate  it 
to  some  extent. 


FahneatocJK  berminats 


In  no  insCance'Shall  Ht. 
height  above  txiffy  of-ttte 
oeil  exceed  4 


No  6  No.4-0 

'resolve:'  'reserve:' 

Dinoensions  are  of  cells  with  paper  covennq  pemored. 

Fig.  1-3. -BATTERY,  RESERVE  DRY  CELLS,  STANDARD  SIZES. 

Referring  to  ligures  1-'J  ;iud  1-;'..  it  will  l»e  noted  that  the  two  sizes  of 
re.serve  dry  cells  cori-espond  in  dimensions  with  cells  of  similar  number  not  of 
tiie  reserve  type,  Tlie  reserve  tyi)e  has  i)ractically  been  adopted  by  the  Signal 
Corps.     The  Xo.  5  size  is  not  a  standard  issue. 

Tlie  v(»ltage  of  a  cell  is  important  and  should  in  no  case  be  less  than  one  volt, 
but  the  internal  resistance  is  of  greater  importance  since  the  cell  which  is 
nearly  exhausted  may  at  times  show  a  conii)iiratively  high  K.  M.  F. 

With  an  Jiiiinieler  c(Hiiiecte(l  directly  to  the  leniiinals  of  a  No.  (>  cell,  new  cells 
should  show  a  reading  of  at  least  15  nniperes  (some  cells  will  show  124).  The 
voltage  reading  of  a  new  cell  on  oj»en  circuit  should  l)e  at  least  1.4. 

.\iiiiiieter  rejuUngs  should  be  accomplished  as  (piicUl.v  as  jiossilile,  as  in  milk- 
ing the  lest  llie  cell  is  jiractically  short  circuited,  the  olimic  resistance  of 
ammeter  being  very  low. 


(6) 


Voltaic  Cell,  Ohm's  Law,  Batteries — -Chapter   1 .  7 

Ordinarily,  dry  cells  tested  in  iifcordaiu*'  with  tlic  above  wiiieli  show  a 
voltage  lower  tliaii  1  or  a  reading  of  aniineter  less  than  2  should  under  no  eir- 
t  innstances  l»e  turned  into  supply  depots  or  transferred  to  accountable  officers. 

The  above  does  not  apply  to  the  reserve  type  of  cell  unless  it  has  been  put  in 
cnnnnission  l>y  the  addition  of  water. 

Dry  cells  in  good  condition  liave  a  voltage  of  about  ].4."i.  The  internal  resist- 
ance and  weights  of  the  various  types  are  aliout  as  follows: 


Size. 

Interna 
resistance. 

Weight. 

Size                        Internal 
resistance. 

Weight. 

4-0 

Ohmx. 
0.2.5 
.25 
.20 
.20 
.12 

Ounces. 
Ill 
9 

IS 

:« 
56 

Ohmx. 
8 0.10 

Ounces. 
SO 

i 

Reserve  4-0 .29 

Reserv    5 .22 

Reserve  6 .19 

Type  A  tungsten  " .30 

Hi 
18 

ti 

32 

7 

8 

'  Internal  resistance  shown  is  for  each  cell  of  the  unit.    Weight  shown  is  for  the  unit  complete,  including 
cardboard  container. 

CLOSED-CIRCUIT    BATTERIES. 

The  gravity,   Fuller,  and   Edison   are   tlie   types   of   closed-circuil   cells   sup- 
plied by  tlie  Signal  Corps. 

Useful  data  on  the  above  cells  is  shown  in  the  following  table: 


Type  of  cell. 

Voltage. 

Weight. 

Internal 
resistance. 

.- 1    -         1.00 

Pounds. 
115 

12 
11 

Ohms. 
3.0 

Fuller . 

2.  on 

.  «7 

.07 

GRAVITY     CELL. 

This  is  the  form  of  i)riinary  cell  most  extensively  used  in  telegraphy  and 
telephony  when  a  small  but  constant  current  is  required.  The  usual  form 
is  sliown  in  figure  1-4. 

These  cells  have  been  furnished  previously  in  two  sizes,  each  l>eing  desig- 
nated by  dimensions  of  containing  jar.  One  size  is  6  by  8  inches  and  the 
other  is  5  by  7  inches.  Tlie  latter  size  has  been  recently  adopted  by  the  Signal 
Corps  as  standard,  and  this  size  only  will  hereafter  be  issued. 

In  the  bottom  of  the  jar  are  placed  three  strips  of  sheet  copper,  riveted 
together,  as  shown  in  figure,  with  a  rubber-insulated  wire  attached  to  one 
of  the  strips.  There  are  many  forms  of  zincs,  but  the  "  crowfoot "  is  the 
form  now  almost  universally  used. 

To  set  up  the  cell,  place  about  3  pounds  of  bluestone  (svilphate  of  copper) 
in  the  cell  after  putting  in  the  copper,  then  hang  the  zinc  and  fill  with 
water.  The  bluestone  should  be  allowed  to  settle  without  any  attempt  to 
dissolve  it  by  stirring  or  other  means.  The  cell  or  cells  are  then  "  short- 
circuited "  (zinc  and  copper  connected  together)  and  allowed  to  stand  sev- 
eral days.  By  that  time  part  of  the  bluestone  will  have  dissolved,  the  blue 
line  being  well  defined.  Above  this  will  be  a  clear  solution  of  sulphate  of  zinc, 
formed  by  the  action  of  the  battery  ;  the  sulphate  of  zinc,  being  of  less  spe- 
cific gravity  than  the  copper  sulphate  solution,  will  remain  on  top  if  the  cell 
is  not  shaken  or  stirred  up.    The  battery  may  now  be  put  into  service. 


(7) 


S  Signal  Corps  Manual  No.  3. — Chapter  1. 

If  in  a  hurry  fur  llie  coll,  it  may  lie  .started  off  at  once  by  stirring  up  about 
a  tablospoonful  of  .salt  with  the  water  before  pouring  it  into  the  cell ;  but 
this  method  is  apt  to  malce  a  battery  dirty  and  considerably  .shorten  its  period 
of  usefulness.  Any  long,  dark  masses  forming  on  the  lower  part  of  the  zinc 
should  be  removed  with  a  stick.  The  zinc  sulphate  solution  will  grow  stronger 
and  stronger,  until  finally  the  -svhite  salts  will  begin  to  creep  or  climb  up  llu' 
sides  of  the  jar  and  the  zinc.  As  they  will  corrode  the  connections  and  ( aus*' 
dirt  and  loss  of  insulation  around  the  cells,  they  should  be  removed.  IVIuch 
of  the  trouble  will  be  obviated  if,  as  soon  as  they  appear,  part  of  the  zinc 
sulphate  solution  is  drawn  off  with  a  battery  syringe  or  a  siphon  made  of 
lient-glass  tube,  and  watiM-  juit  in  its  i»lac(>.     If  the  upper  parts  of  the  cells  are 


Fig.    1-4.— BATTERY  CELL,   GRAVITY. 


Part 
No. 


Name. 


lleference 
No. 


.Tar,  glas.s 

Crowfoot,  zinc 

Strips,  copper  v.'itli  lead 

Hluestone,  1  charge  (3  pounds). 


wanned  an<l  smeared  wilh  iiaraflin  if  will  heli)  mailers.  I'.nt  the  besl  jilan  of 
preventing  evaporation  and  criH'iiing  of  salts  is  to  use  a  good  <piality  of  parallin 
or  lubricating  oil,  pouring  on  a  layer  about  one-fonrlii  inch  (hick  as  soon  as  Hie 
•  ells  are  set  up.  In  cleaning  cells  after  that,  wet  cottnii  waste  (lipped  in  sand 
will  cIcMii  tlio  zincs,  etc.,  of  the  adhering  oil.  As  .soon  as  the  bine  solution  goes 
down  below  the  level  of  the  copjier  more  bhH>stone  slionid  be  ailded.  (/orrosion 
oC  the  connections  of  the  zincs  with  their  wires  shotdd  be  carefidly  looked  after. 
It  is  betler  to  have  routine  insjiec-t ions  of  batteries  made,  and,  if  practicable, 
instrumental  tests  ijiade  wilh  the  voltmeters  or  voltaninieters.  r>y  (his  means 
deterioration  may  bi'  acfiiiati'ly  noted  and  many  annoyances,  breakdowns,  and 
delays  which  are  fr<-(piently  due  to  neglect  and  lack  of  regular  inspection  of 
(he  l»atterle.s  may  l>e  av(»ided. 

The   internal    resistance   of  a    gravity    cMl    in    good    condition    will    be   found 
to  be  about  3  (duns,  its  E.  M.  F.  1  volt. 

(8) 


Vdtaic  Cell,  Ohm's  Law,  Batteries — Chapter   1 .  9 

ni.l.EU    IJAITKUV. 

Tills  helonjis  to  the  class  poimlaily  called  "  aeid  batteries."  The  cell  has 
a  hi^li  electromotive  foree,  a  eoinparalively  low  internal  resistance  ((>..")  olun), 
and  is  much  used  as  transmitter  battery  on  lonj;-distance  heavily  w(n-ked  tele- 
phones or  local  battery  telephone  switchboards.  Its  only  disadvantafre  is  that 
it  uses  a  corrosive  solution  containinji  suli»huric  acid,  necessitatinj,'  nuich  care 
in  handling.  It  consists  of  a  glass  jar  about  8  inches  high  and  6  inches  in 
diameter,  with  a  wooden  cover  treated  with  asphaltum  or  P.  &  B.  paint. 
(Fig.  !-.">.)  This  supports  a  carbon  plate  ;ili«iul  4  inches  wide,  9  inches  long, 
and  one-t'ourth  inch  thick,  with  tlie  (op  c(iat<'d  with  pui-aHin  to  prevent  the  cor- 


Fig.  1-5.— BATTERY  CELL,  FULLER. 


Part 
Xo. 


Name. 


Reference 
No. 


Jar,  glass 

Cover,  wooden  with  carbon  plate. 

Porous  cup 

Zinc  conical,  with  wire 

Mercury,  2  ounces 

Chromic,  1  charge  (1  pound). . . . . 


rosion  of  the  connection  liy  the  acid.  In  the  jar  stands  an  earthenware  porous 
cup  7i  by  3  inches,  in  the  bottom  of  which  is  placed  about  2  ounces  of.  mercury. 
In  this  stands  a  conical  zinc  cast  to  a  copper  wii-e  which  extends  out  at 
the  top.  In  the  glass  jar  is  placed  the  "  electropoion "  solution,  luade  by 
slowly  adding  1  pound  of  strong  sulphuric  acid  to  9  pounds  of  distilled  water, 
and  then  stirring  in  3  pounds  of  pulverized  bichromate  of  potash  or  2^  pounds 
of  bichromate  of  sodium.  This  last  is  preferable,  as  the  crystals  formed  in 
the  action  of  the  cell  are  not  so  hard  and  insoluble  as  those  produced  by  the 
potasli.  In  the  porous  cell  with  the  zinc  and  mercury  is  placed  water  in 
which  about  n  tablespoonful  of  salt  has  been  dissolved.     This  (;ell  will  usually 


(9) 


10 


Signal  Corps  Manual  No.  3. — Chapter  1. 


require  little  attention  for  three  or  four  mouths.  When  the  solution  assumes 
a  muddy  bluish  tint  it  is  about  exhausted. 

If  the  copper  wire  at  its  junction  with  the  zinc  is  covered  with  paraffin  or 
ozite,  or  if  the  copper  wire  is  well  amalgamated  by  rubbing  with  mercury 
after  dipping  it  into  acid,  the  wire  does  not  tend  to  be  eaten  off  at  the  junction, 
as  it  otherwise  does  under  heavy  service.  The  Signal  Corps  issues  the  ma- 
terials for  the  solution  in  <lry  form,  which  when  dissolved  form  the  electrolyte. 
This  is  purchased  under  various  commercial  names  as  chromac,  voltac,  chro- 
mite,  salts,  etc.,  the  first  being  the  usual  designation.  It  is  packed  in  tin  cans 
with  thin  cut-out  top,  containing  1  pound,  which  is  the  amount  for  one  charge. 
Full  directions  for  using  are  marked  on  each  can. 

The  carbon  of  this  cell  lasts  indetinltely,  but  should  be  soaked  in  warm 
water  when  renewals  are  made.  The  zinc  may  last  through  several  renewals 
of  the  electropoion  fluid.     The  mercury  should  be  saved  and  used  repeatedly. 

The  following  table,  cpioted  from  Alibdtfs  Telepliony,  indicates  the  effect  of 
age  on  efficiency  of  transmission  with  the  Fuller  cell. 

Two-veil  Fuller  battery. 


Volume  of 

Volume  of 

Age. 

transmis- 

Age. 

transmis- 

sion. 

sion. 

Days. 

Per  cent. 

Days. 

Per  cent. 

20 

92 

60 

7(i 

30 

88 

70 

70 

40 

84 

80 

li2 

50 

80 

90 

54 

From  this  it  would  appear  that  the  (vlls  nuist  be  renewed  at  least  once  in 
three  months  when  used  on  a  telephone  transmitter. 

EDISON    PRIMARY    BATTERY. 

The  type  V  cell  shown  ui  figure  1-6  is  the  standard  Edison  cell.  As 
previously  manufactured  for  the  Signal  Corps,  it  has  the  same  capacity  as 
the  old  Edison  La  Lande  cells,  but  its  enameled  steel  jar  was  slightly  conical, 
enabling  the  cells  to  be  nested  together  for  transportation.  The  caustic  soda 
and  oil  for  each  cell  are  issued  in  tin  cans,  so  that  there  is  nothing  that  will 
not  stand  transportation.  This  cell  has  a  very  low  internal  resistance  (not 
exceeding  one-eighth  ohm)  and  will  i-ciiiain  s(>t  up  on  open  circuit  for  a  long 
time  without  ai)preciable  depreciation.  It  has  a  capacity  of  about  1.10  ampere 
hours,  which  means  that  it  will  furnish  about  210  days'  continuous  service 
on  a  line  where  the  curn-nt  is  HO  niilliamperes  and  40  days'  service  when  the 
current  is  about  O.ifi  ampere. 

If  gives  but  0.67  volt  E.  M.  F.  in  stoady  worU. 

The  following  complete  directions  fur  setting  up.  niMnagcmcnt,  and  ronewal 
of  these  cells  are  furnished  by  the  conii»any  nianutactnring  tlit-ni: 

DIBKCTIONS    FOR    HKTTING     IP    AND     USING    KDISON     PUIMAHY     HATTKRY,     KNOWN     AS 

EDISON    CELL,    TYPE    V. 

TO     CHARGE     AND     CONNECT     BATTERIES. 


To  wake  Holutinn. —  Fill  tlic  colls  with  water  to  H  indies  of  the  top. 
Add  the  caustic  sotla  gra<lually  to  the  water,  stirring  until   the  soda  is  en- 
tirely dis.solved. 

(10) 


Voltaic  Cell,  Ohm's  Law,  Batteries — Chapter   1 , 


11 


When  the  solution  cools,  more  water  should  lie  added  to  hrln^  it  up  to  li 
inches  of  tlie  top.  Then  pour  contents  of  bottle  of  heavy  paraflin  oil  from 
bottle  furnished  for  each  jar  on  the  solution. 

NoTK  1. — The  caustic  soda  will  burn  the  skin  and  clothes.  In  stirring  the 
litiuid,  avoid  splashing  it. 


Fig.   1-6.— BATTERY  CELL,    EDISON   PRIMARY  TYPE   V. 


Jar,  enameled  steel 

Cover  for  jar 

Plate ,  oxide 

Copper  bolt 

Copper  nut 

Thumb  luit 

Jamb  nut 

Double  /-inc  plate 

Leather  washer 

Insulating  tubes,  hard  rubber 
Frame 


C. 

F. 

G. 

H. 

N,A. 

M,D. 

Z. 

E. 
B. 


To  act  up  rrllfi. — Unscrew  the  nut  .Y  and  the  .ianil>  nut  V  from  the  screw  on 
tlie  brass  neck  of  the  double  zinc  jilate  and  remove  tlie  leather  washer.  I'ass 
tlie  screw  from  below  through  the  central  hole  in  the  cover  (\  lieplace  the 
leather  washer  and  the  .iamb  nut  .1/  on  the  screw  and  tighten  down  the  jamb 
nut  until  the  zinc  plate  is  rigid  to  tlie  cover.  The  thumb  nut  .Y  can  then  be 
screwed  on.  ' 

Unscrew  the  nuts  A  A  and  jamb  nut  />  from  the  screws  on  tin*  two  side 
])ieces  B  B  of  the  co])per  frame,  leaving  the  tlat  leather  washers  in  i>osition 
on  the  screws,  and  jiass  the  screws  from  below  through  the  two  round  boles 
in  the  cover  (\  Keiilace  the  jamb  nut  on  one  of  the  .screws  and  one  of  the 
Ihumb  nuts  on  the  other  screw,  and  tighten  both  down  until  the  frame  sides 
Jire  rigidl.v  clamped  to  the  cover.  lit^place  the  other  thumb  nut  on  the  screw 
holding  jamb  nut.  Then  slip  the  hard  rubber  insulating  tubes  E  E  over  the 
sides  of  the  frame,  one  on  each  side. 

To  fill  coiiinr  f rallies.- — (In  this  cell  only  one  oxide  plate  is  used.)  (See 
fig.  1-6.)  Slide  the  oxide  plate  /'  suflicieutly  far  into  the  fi-ame  to  enable  the 
copper  bolt  (7  to  be  passed  underneath  it  through  the  slots  in  the  bottom  of  the 
frame  sides  and  the  copper  nut  H  tightened  up  on  same. 


4(3581^—17- 


(11) 


12  Signal  Corps  Manual  No.  3. — Chapter  1. 

Be  careful  that  the  zinc  plates  do  not  touch  the  copper  oxide  plates  or  the 
cell  will  he  short-circuited. 

The  copper  connection  is  made  between  the  thumb  nut  A  and  the  jamb  nut 
D  on  one  end  of  tlie  copper  frame  and  the  zinc  connection  between  the  thumb 
nut  A"  and  the  jamb  nut  .1/  on  the  brass  bolts  suspending  the  zincs. 

After  the  oxide  and  zinc  plates  are  properly  connected  to  the  cover,  as  above, 
soak  them  in  water  and  while  still  wet  insert  in  jar  filled  with  caustic  solution. 

(Wetting  the  plates  prevents  the  oil  in  jar  from  adhering  to  them.) 

Important. — In  order  to  allow  the  cover  on  the  jar  to  fit  easily,  it  is  ad- 
visable to  wet  the  rubber  gasket  ring  fitting  into  the  grooved  edge  of  the 
cover  by  placing  it  in  water.  This  will  cause  the  cover  to  slip  on  easily  and 
will  make  the  cell  liquid  tight. 

It  is  absolutely  necessary  that  the  upper  edge  of  the  oxide  plates  should  be 
submerged  at  lea.st  1  inch  below  the  surface  of  the  caustic  soda  soluticin  in  the 
jar ;  also  on  no  account  can  the  layer  of  oil  on  top  of  the  solution  be  omitted. 

RENEWING. 

When  the  cell  becomes  exhausted  the  solution  and  the  remains  of  the  zinc  and 
oxide  plates  must  be  thrown  away.     The  renuiining  parts  can  be  used  again. 

TO  TAKE  THE  CF.LLS   APART. 

Lift  the  lids,  tmscrew  the  bolts,  and  remove  the  zincs  and  oxide  plates.  Wash 
off  (with  water)  the  copper  frames,  bolts,  and  rubber  insulators,  brightening  up 
the  metal  where  corroded  with  emery  paper,  especially  the  inside  grooves  of  the 
copper  frame  sides.  I'our  away  the  solution  carefully  and  set  up  cells  with  new 
caustic  soda,  oxide  plates,  and  zincs  according  to  directions. 

Note. — In  taking  the  cells  apart  the  parts  that  have  been  immersed  in  the 
caustic  soda  must  be  washed  before  they  are  handled. 

TO    ASCERTAIN    IF   THE    OSIDiC    PLATES    ARE    EXHAUSTED. 

Pick  into  the  body  of  the  oxide  plates  with  a  sharp-pointed  knife.  If  they  are 
red  throughout  the  entire  mass,  they  are  comi)letely  exhausted  and  need  re- 
newing. If  on  the  contrary,  there  is  a  layer  of  black  in  the  interior  of  the  plate, 
there  is  still  some  life  left,  the  amount  being  dependent  entirely  upon  the  thick- 
ness of  the  layer  of  black  oxide  still  remaining. 

COPPUR   FliAME.S. 

When  renewing  I  he  battery  it  is  desirable  1o  clean  (he  inside  grooves  of  the 
coitjier  frames.  wJiere  the  copper-oxide  jtiates  make  conlact.  so  as  to  insure  a 
good  electrical  comiectit)n.  This  is  es]teci;illy  imi»ortant  when*  the  batteries 
iire  recpiired  to  give  a  heavy  current  for  caulery  or  motor  itun><>ses.  These 
frames  can  be  easily  cleaned  by  wrapi)ing  a  small  pi(>ce  of  emery  paper  around 
a  slick  which  will  just  lit  into  the  groove,  or  by  inmiersing  lliem  in  a  dilute 
solution  of  1  part  of  sulphuric  acid  and  4  parts  Wiiter.  iind  then  cnrefnlly 
rinsing  them  in  clean  water  to  nMiiovt^  all  traces  of  the  acid. 

(Uiution. — The  oxide  plates  should  never  be  remove<l  from  the  caustic  .soda 
solution  and  allowed  to  dry  in  the  air.  as,  if  this  is  done,  the  surface  of  the 
plates  becomes  oxidized  by  absorbing  tlu>  oxyg(Mi  from  (lie  air,  and  the  oxide 
thns  formed  is  mucii  nn»re  didicult  of  reduction  than  the  original  oxide  of  which 
(he  plates  are  formed.  The  internal  resistance  is  consetiueiitly  vei-y  greatly  in- 
creased and   the  ciii'i'<'nt    materially  diminished. 

.NoTK. — Where  batteries  are  jilaced  in  warm  plac(>s  they  should  be  examined 
every  (wo  or  three  months  to  see  (hat  the  solution  has  not  evaporated,  as  this 
will  gradually  lake  i)lace,  in  sjiile  of  the  oil,  if  they  are  in  a  Iio(  room.  If  the 
solntion  is  founrl  to  have  evaporated,  add  more  water  to  bring  it  again  to  the 
I)roper  height.  It  is  of  (he  first  im|ior(ance  that  all  ))inding  posls  and  connect- 
ing wires  should  be  kept  clean  and  lii-iglil  at  the  jioints  of  connection. 

The  (ype  V  cell  is  excelleni  for  nse  as  an  ignition  battery  or  in  lieu  of  small 
capacity  storage  batteries  where  no  charging  current  exists.  The  Signal  Corps 
uses  (his  type  of  ba(tery  quite  extensively  in  comiection  with  the  Alaska 
Military  ('able  and  Telegraph  System. 

(12) 


Voltaic  Cell,  Ohm's  Law,  Batteries — Chapter   1 . 


13 


GROUPING   OF   CELLS. 

When  it  is  necessary  to  cause  a  certain  current  to  flow  through  a  con- 
siderable resistance,  as  a  long  telegraph  line,  for  instance,  the  necessary 
E.  M.  F.  is  obtained  by  connecting  cells  in  series — that  is.  the  copper  of  one 
cell  to  the  zinc  of  the  next,  and  so  on  until  the  requisite  E.  M.  F.  is  obtained, 
tlie  relatively  small  increase  of  the  total  resistance  due  to  the  internal  resist- 
ance of  the  cells  being  of  little  effect.  The  total  voltage  is  the  sura  of  the 
voltages  of  all  the  units  so  connected.  But  when  it  is  desired  to  get  a  certain 
current  through  a  low  resistance,  another  grouping  must  be  made.  The  in- 
ternal resistance  of  the  ordinary  gravity  cell  is  about  3  ohms.  And  with 
its  one  volt  E.  M.  F.  the  current  through  a  short  thick  wire  of  no  appreciable 
resistance  connecting  its  poles  will  l)e  one-third  ampere.     And  if  we  have  100 


Fig.   1-7.— BATTERY  CELLS  CONNECTED    IN    SERIES. 

cells  in  series  and  connect  the  terminals  of  the  entire  battery,  we  would  get 
ifg  ampere,  or  one-third,  as  before.  For  any  number  of  these  cells  in  series, 
to  obtain  an  increased  current  through  low  external  resistance,  we  must  cut 
down  tlie  internal  resistance  of  our  battery.  This,  with  a  given  type  of  cell, 
may  be  done  by  linking  them  in  parallel — that  is,  by  connecting  all  the  zincs 
together  and  all  the  coppers  together  and  then  connecting  the  multiple  zinc 
and  multii)lo  copper  thus  obtained  to  the  low  external  resistance.     The  E.  M.  F". 


+ 


Fig.   1-8.— BATTERY  CELLS  CONNECTED    IN    MULTIPLE. 

of  tlu'  battery  remains  the  same  as  that  of  one  cell,  but  the  current  output 
is  now  e(iUMl  to  the  sum  of  the  current  capacities  of  all  the  units  .so  connected. 

Figure  1-7  shows  four  cells  of  battery  connected  in  series  and  figure  1-8 
shows  four  cells  of  battery  connected  in  multiple,  or  parallel  as  it  is  sometimes 
called. 

In  the  first  case  we  should  get  a  current  of  ^^  =  1  ampere  through  our 
short  circuit;  and  in  the  second  case,  I=l^i=i  ampere. 

While  in  botli  figures  the  gravity  cell  is  shown,  the  rule  is  applicable  to  any 
type,  class,  or  make  of  primary  or  secondary  battery  cells. 

(13) 


14  Signal  Corps  Manual  No.  3. — Chapter  1. 

Number  and  kinrl  of  hattcrij  cells  required  by  various  apparatus. 
(Where  more  than  one  battery  cell  is  indicated  the  cells  are  invariably  connected  in  series.] 


Instrument. 


Cell. 


L.  B.  post-telephone  switchboard  i {puller  ^ 

Camp  s\\-itchboard No.  6  reserve 

L.  B.  telephone,  pos^  telephone  system do 

Camp  telephone ; Type  A  tungsten. 

Service  buzzer I.... .do 

Induction  telegraph  set do 

Test  buzzer  for  radio  pack  set do 

Flash-light , do 


Number  of  cells. 


3. 
2. 
2. 
2. 

1  unit  (2  cells). 

2  units  (4  cells). 

Do. 
Do. 
1  unit  (2  cells). 


I  Either  gravity  or  Fuller  may  be  used  for  operator's  transmitter  circuit.    In  addition,  2  cells  of  No.  6 
reserve  may  be  used  for  night  alarm. 

Secondary  Batteries. 

The  storage  battery  differs  from  the  primary  battery  in  its  action  in  tliat 
when  it  has  given  out  all  the  energy  the  chemicals  present  enable  it  to  supply, 
instead  of  requiring  new  elements,  the  cell  can  be  completely  regenerated  or 
brought  back  to  its  original  charged  condition  by  passing  a  current  into  it  in 
a  direction  opposite  to  that  in  which  the  flow  took  place  on  discharge. 

Although  there  are  many  combinations  which  can  be  used  for  storage  bat- 
teries, a  large  majority  of  those  in  commercial  use  and  all  those  installed  by 
the  Signal  Corps  are  of  the  lead-sulphuric  acid  type,  which  in  its  basic  prin- 
ciple consists  of  two  especially  prepared  dissimilar  lead  plates  immersed  in 
diluted  sulphuric  acid.  Each  cell  of  the  lead-sulphuric  acid  storage  battery 
has  an  E.  M.  F.  of  about  2.05. 

The  Edison  storage  battery  which  has  recently  been  developed  and  placed  on 
the  market  makes  use  of  oxides  of  nickel  and  iron  in  the  positive  and  negative 
electrodes  respectively.  The  grids  supporting  the  active  material  are  made 
of  nickel-plated  steel,  and  the  electrolyte  is  a  solution  of  caustic  potash  and 
water.  These  cells  when  fully  charged  have  a  normal  E.  M.  F.  of  1.2  volts 
and  are  charged  at  about  1.7  volts.  They  stand  abuse  much  better  than  the  lead- 
sulphuric  type  of  battery  and  are  highly  advantageous  for  vehicle  purposes,  as 
it  is  claimed  the  output  per  unit  of  weight  is  nearly  twice  that  of  lead  cells. 
An  idea  of  tlie  ruggedness  of  this  battery  can  be  imagined  when  consideration 
is  given  to  the  fact  that  when  the  battery  becomes  unhealthy  or  impaired  by 
liick  of  work,  or  t«»o  nnich  work,  s'.iort  circuiting  tl\ebattery  for  a  moderate  pcritxl 
will  assist  in  returning  the  btittery  to  a  healthy  condition. 

Secondary  batteries  in  the  form  of  storage  battiTies  or  accunudators  tire  used 
by  the  Signal  Corps  for  supplying  necessary  cuiMcnt  in  coiuiection  with  com- 
l)aratively  large  telephone  systems,  signaling  systems.  mihI  teiegrapli  systems 
where  a  suitidile  charging  circuit  is  available.  When  used  for  sui)plying  cur- 
H'nt  for  the  oi)eration  of  post  telephone  .systems,  the  system.s  are  invariably 
what  are  termed  "common-liattery"  or  "central-energy"  systems.  With  this  type 
of  .system  the  current  for  operation  of  all  ai)paratus  is  obtained  from  one  bat- 
tery. Ill  a  local-battery  telephone  system  llie  swildiltoard  and  e;ich  telephone 
is  e(|uijiiiei|  with  ;i  l)attery. 

Ill  lii-c-(((iil  i-o|  systems  :il  seaconst  defenses  1."  cells  of  storage  hatlery,  con- 
nected ill  .series,  are  installe<l  for  siiitplying  <-m'rent  for  operation  of  (he  telephone 
.system  of  (he  fire-control  system  pro|>er.  and  in  a  great  many  in.stances  (he  same 
battery    furnishes    current     n«'ce.ssiny     in    the    oj»erati<)n    of    the    entire    post 

(14) 


Voltaic  Cell,  Ohm's  Law,  Batteries — Chapter  1.  15 

t('lei)liono  system.  In  emorgoiicy  the  saiue  battery  may  also  he  used  to  siijiply 
Jill  signal  apparatus  of  the  fire-control  system,  which  nornjally  is  supplied  by 
current  obtained  from  a  motor  generator  set,  the  motor  generator  set  lieing 
used  to  charge  the  storage  battery  when  oiieration  of  tlie  system  is  not  in 
progress. 

Either  a  battery  of  12  cells  (jr  a  battery  of  15  cells  of  storage  battery,  con- 
nected in  series,  are  installed  for  supplying  necessary  current  for  operation  of 
common-battery  post  telephone  systems  at  interior  posts. 

General  Data  Concerning  the  Storage  Battery. 

The  elementary  form  of  storage  cell  is  made  by  innnersing  two  lead  plates 
in  dilute  sulphuric  acid.  The  principle  inv(jlved  in  the  storage  cell  is  the 
chemical  action  produced  by  a  current  which  causes  such  changes  of  the 
lead  plates  in  the  acid  that  upon  cessation  of  the  current,  if  the  two  plates 
are  connected  together  by  a  wire,  a  current  will  flow  in  the  opposite  direction 
from  the  original  one  and  the  plates  will  tend  to  return  to  their  original 
condition. 

The  action  of  the  current  is  to  coat  the  plate  that  is  connected  with  the 
positive  pole  of  the  charging  dynamo  with  pentxide  of  lead,  and  to  reduce 
to  spongy  metallic  condition  the  surface  of  the  plate  connected  with  the 
negative  pole.  When  the  plates  are  connected  by  a  wire  the  peroxide  coating 
tends  to  be  reduced  back  to  lead  and  the  spongy  lead  on  the  other  plate  to 
become  oxidized.  The  plates  thus  becoming  alike  the  current  will  cease  and 
the  cell  is  said  to  be  discharged.  Various  methods  of  manufacture  are  in- 
tended to  give  the  plates  more  capacity;  that  is,  to  prepare  more  reducible 
peroxide  on  one  and  more  spongy  lead  on  the  other.  The  means  adopted  are 
to  make  the  plates  up  in  the  form  of  tine  strips  (tr  grids  of  lead  and  till  in 
these  interstices  with  the  oxides  of  lead  by  various  processes.  These  plates, 
being  made  up  in  sets,  are  then  innnersed  in  acid  and  given  what  is  called 
a  "  forming  charge,"  after  which  they  may  be  used. 

The  plates  as  receivetl  fi'om  the  manufacturer  are  of  two  kinds.  The 
.sets  of  plates  of  one  kind  are  of  a  chocolate  brown,  while  the  other  sets  are 
of  a  grayish  leaden  color.  When  these  are  placed  in  the  jars  the  .sets  (jf 
I)lates  represent  the  zinc  and  copper,  respectively,  of  a  primary  battery,  the 
gray  plates  acting  as  zincs  and  the  brown  as  copper.  In  connecting  cells  in 
series  the  brown  .set  of  one  cell  should  be  connected  with  the  gray  .><et  of  an- 
other, and  so  on.  Care  should  l>e  taken  that  no  plates  of  different  kinds  touch 
on  the  inside  of  cells,  and  that  the  separators  are  properly  placi'd,  if  these 
are  furnished  with  the  kind  of  cell  use<l.  The  connecting  lugs  should  all  be 
brightened  before  they  are  bolted  t<tgether,  and  after  all  connections  are 
made  it  is  well  to  go  over  them  with  a  coating  of  cosmoline  or  sisphaltum 
varnish.  The  cells  should  always  be  set  up  in  a  dry  place,  preferably  where 
there  is  a  good  means  of  lighting  and  where  there  may  be  ample  ventilation. 

The  first  or  initial  charge  of  any  storage  battery  takes  a  nuich  greater 
length  of  time  than  the  subsequent  regular  charges.  The  initial  charge  of  any 
make  of  storage  battery  shoxild  be  continuous  if  possible.  With  most  bat- 
teries it  takes  from  50  to  60  hours  to  complete  the  initial  charge,  while  the 
regular  charge  thereafter  should  be  completed  in  approximately  eight  hours 
at  the  normal  rate.  The  battery  should  not  be  discharged  below  1.70  volts 
per  cell. 

Purity  of  electrolyte  is  of  first  importance  in  storage  battery  oi>eration, 
and  all  acid  should  be  tested  where  a  douljt  as  to  its  purity  exists. 

(15) 


16  Signal  Corps  Manual  No.  3. — Chapter  1. 

TESTS    FOR    PURITY    OF    ELECTROLYTE. 

The  necessity  for  using  pure  electrolyte  in  storage  batteries  is  sometliing 
whicli  is  seldom  recognized.  Its  importance  in  maintaining  a  battery  in  its 
highest  efficiency  for  any  length  of  time  is  a  matter  which  sliouhl  receive 
attention,  not  only  at  the  time  the  battery  is  set  up  but  subsequently,  in  the 
addition  of  water  or  fresh  electrolyte. 

The  most  frequent  impurities  in  water  are  sodium  or  magnesium  chloride, 
and  some  of  the  salts  of  lime  and  iron.  The  presence  of  lime  will  of  course 
be  objectionable,  but  its  presence  in  very  small  quantities  is  less  objectionable 
than  that  of  the  other  impurities. 

In  general,  it  may  be  stated  that  the  only  suitable  water  for  safety  is 
distilled  water,  and  no  amount  of  trouble  necessary  to  get  this  kind  of  water 
should  be  considered  as  too  great  when  making  up  the  electrolyte  if  strong 
acid  be  furnished,  or  for  subsequent  additions  to  replace  loss  by  evaporation. 

Of  course  all  dry  reagents  should  be  dissolved  only  in  distilled  water  in 
preparing  for  tests.  Unless  otherwise  stated,  the  testing  solutions  should 
be  about  one-half  saturated. 

If  strong  acid  is  furnished,  the  method  of  mixing  this  with  the  requisite 
amount  of  water  to  bring  the  specific  gravity  of  the  solution  to  1.210,  is  stated 
later.  It  is  urged  that  no  aciil  be  useil  which  is  made  from  iron  pyriti's ;  the 
only  suitable  electrolyte  is  nuule  from  acid  which  is  manufactured  from  pure 
sulphur. 

The  impurities  which  may  be  in  the  acid,  and  for  which  tests  shoiild  be 
made,  are :  Chlorides  or  free  chlorine,  the  salts  of  iron,  copper,  mercury,  and 
the  nitrates.  Small  cases  of  reagents  may  be  furnished  by  the  Signal  Corps 
for  storage-battery  installations  where  there  are  15  cells  and  upward,  and 
tests  should  be  made  before  setting  up  the  battery  and  in  subsequent  addi- 
tions of  electrolyte  if  a  doubt  as  to  its  purity  exists. 

It  must  be  noted  that  after  running  some  time  the  electrolyte  may  becinne 
contaminateil  with  cldorides  or  nitrates  from  the  plates,  formed  dm-ing  man- 
ufacture. 

The  sniallreagent  cas(>  (lig.  1-0)  is  furnished  for  testing  t'li'ctrolyte.  The 
contents  of  tiiis  case  are  shown  in  the  parts  list  of  tiu»  illustration. 

If  distilled  water  is  used,  of  course  no  tests  <tf  it  will  be  necessary,  but  any 
natural  water  should  be  open,  to  suspicion. 

Tests  for  chlorine  or  ehlorUJes. — A  few  (h'ops  of  solution  of  nitrate  of  silver 
in  a  test  tube  partly  filled  witli  elccti-olyle  will  give  a  curdy,  white  precipitate 
of  silver  chloride  if  chlorin(>  or  its  salts  are  iiresenl.  This  chloride  turns  to  a 
violet  tint  on  exposure  to  light.  If  the  cleai-  licpiid  be  jtoured  off  and  strong 
ammonia  added  to  the  white  i)ri'cipitate,  it  w  ill  dissolve. 

Test  for  iron. — The  presence  of  ferrous  salts  in  the  ehvfrolyte  is  shown  if  a 
dark-bine  precii)itate  is  given  upon  the  addition  of  a  solution  of  the  i-ed  i)rnssiate 
ol  jHitassium.  If  fei'rif,-  salts  are  i)resent  in  the  electrolyte*,  a  solution  of  yellow 
prussiate  of  jtotassiuni  will  give  a  blue  tint,  (^on.seepu'ully,  if  into  two  test 
tubes,  one  of  which  contains  a  few  drops  of  y<'llow  ])rnssiale  and  the  other  a 
few  drops  of  red  prussial(>,  a  little,  electrolyte  be  poured,  the  two  tests  can  be 
made  at  once.  If  the  impurities  be  ))reseiit  in  siii.-ill  (|n:intilies  there  will  not 
be  a  precii)ilate  formed,  but   a  hluish-gi-een  (•(ihii'al  ion  will   i-esult. 

Test  for  eopper. — Place  a  small  (piantity  of  electrolyte  in  a  test  tube  and  add 
an  excess  of  strong  ammonia.  If  coiii)er  be  present  tliere  will  l)e  a  bright 
bluish   tint   given    to   the   mixture.      If  present    in   large  (pianlities,  a   chocolate- 

(16) 


Voltaic  Cell,  Ohm's  Law,  Batteries — Chapter   1 , 


1 


colored  substance  will  be  formed  upon  the  addition  of  a  solution  of  the  j'ellow 
prussiate  of  potassium. 

Test  for  mercury. — The  luercurous  salts  will  {^ive  an  olive-green  precipitate 
with  iodiile  of  potassium ;  the  mercuric  salts,  a  scarlet  precipitate  with  the 
same  reajient. 


Fig.  1-9.— CASE,    REAGENT. 


Part 
No. 


Name. 


Reference 

No. 


Acid,  sulphuric,  8  ounces 

Aqua  ammonia,  8  ounces 

Bottles,  stoppered,  glass 

Case,  wooden 

Diphenylamiiie,  \  ouneo 

Iodide  of  potassium,  J  ounce 

Prussiat  e  of  pot  ash,  red ,  h  ounce 

Prussiate  of  potash,  yellow,  i  ounce. 

Silver  nitrate,  i  ounce 

Tubes,  reagent']  stoppered 

Tubes,  testing,  4 


The  use  of  hydrometers  having  mercury  in  the  lower  bulb  will  frequently 
give  a  mercury  impurity  in  the  electrolyte  through  breakage  of  this  bulb.  Con- 
sequently it  is  better  to  use  only  a  shot-filled  hydrometer. 

Test  for  nitrates. — Some  hiphenylamine  slioidd  l)e  dissolved  in  a  small  quan- 
tity of  concentrated,  chemically  pure,  sulpluu-ic  acid  and  put  in  a  test  tube.  A 
small  quantity  of  electrolyte  is  tlien  carefully  dropped  in  the  same  tube.  If  a 
blue  color  results,  nitrates  or  nitrites  are  present.  Traces  of  nitrates  are  very 
ob.iectionable.    They  cause  a  surprisingly  rapid  deterioration  of  the  plates. 

The  following  instructions  relative  to  installing  and  initial  charge  of  storage 
batteries  is  furnished  by  the  Electric  Storage  Battery  Co.,  of  Philadelphia : 

(17) 


18  Signal  Corps  Manual  No.  3. — Chapter  1. 

UNPACKING  AND   CARE   OF   MATEKIAL. 

1.  Great  care  should  be  taken  in  the  unpacking  and  subsequent  handling  of 
the  various  parts  of  the  liattery,  as  many  of  them  are  easily  broken  or  bent  out 
of  shape  by  rough  handling. 

2.  Open  the  crates  or  packing  boxes  on  the  side  marked  "Up"  and  carefully 
lift  out  the  contents ;  never  slide  out  by  turning  crate  on  its  side. 

3.  As  the  contents  of  each  box  or  crate  is  removed,  carefully  count  the  parts 
and  check  with  the  shipping  list.  A  number  of  small  parts  will  usually  be 
found  in  each  shipment,  and  care  should  be  taken  to  examine  packing  to  make 
sure  that  no  parts  have  been  overlooked.  All  material  should  be  carefully  ex- 
amined for  breakage.  Cracked  or  broken  jars  must  not  be  installed.  No  claim 
for  damage  in  transit  will  be  considered  and  no  claim  for  shortage  will  be 
adjusted  unless  accompanied  by  a  memorandum  showing  the  number  of  case  or 
package,  as  a  record  of  all  cases  by  number  is  carefully  preserved  by  the  com- 
pany, showing  the  exact  contents  of  all  packages,  the  contents  having  been 
double-checlved  before  shipment. 

4.  The  wood  separators  (sheets  and  dowels)  which  have  been  given  a  special 
treatment  are  shipped  wet,  and  they  should  be  kept  so  until  installed  in  the 
battery,  and  not  allowed  to  dry  under  any  circumstances.  If  there  is  any 
delay  in  setting  up  the  battery,  the  sheets  arid  dowels  should  be  left  in  the 
packing  cases  and  kept  wet  by  being  frequently  sprinkled  with  water  at  least 
once  a  week,  the  lid  of  the  case  being  removed  while  sprinkling.  If  a  supply 
is  to  be  kept  on  hand  for  any  length  of  time,  they  should  be  kept  completely 
immersed  in  a  vessel  of  water  to  which  electrolyte  of  1.210  specific  gravity  has 
been  added  in  the  proportion,  by  volume,  of  one  part  of  electrolyte  to  nine  or  ten 
parts  of  water.  The  vessel  (which  must  not  be  of  metal)  should  be  covered 
to  keep  out  impurities. 

ELECTROLYTE. 

5.  The  electrolyte  shipped  with  a  battery  is  dilute  sulphuric  acid  of  a  specific 
gravity  of  1.210  or  2o°  Baume  (except  fen*  type  I^  cells,  see  note)  as  shown  on 
the  hydrometer  at  a  temperature  of  70°  F.  If  it  is  not  convenient  to  procure  the 
electrolyte  from  the  Electric  Storage  Battery  Co.,  already  mixed  and  ready  for 
use,  it  may  be  prepared  by  diluting  sulphuric  acid  of  1.840  specific  gravity  or 
6G°  Baume  (oil  or  vitriol),  which  has  been  made  especially  for  storage  battery 
use,  with  pure  water  (preferably  distilled)  in  the  pi"oi)ortion  of  one  part  acid 
to  four  and  one-third  of  water  by  volume;  1.4(10  specific  gravity  acid  may  be 
reduced  to  1.210  specific  gravity  by  mixing  equal  volumes  of  the  acid  and  pure 
water.  It  is  absolutely  es.sential  that  both  the  acid  and  water  should  be  practi- 
cally free  from  inqiurities  such  as  iron,  nitric  or  hydrochloric  acid.  When  mix- 
ing, slowly  pour  the  acid  into  the  water  (not  the  water  into  the  acid)  and 
thoroughly  stir  with  a  wooden  paddle.  The  final  specific  gravity  must  be 
read  when  the  solution  is  cool.  A  metal  vessel  nuist  not  be  used  for  mixing 
or  handling  the  solution;  a  glazed  (»r  earthenware  crock  or  a  lead-lined  tank  is 
suitai)le,  or  a  wooden  vessel  which  has  not  been  used  for  any  other  purjiose.  such 
as  a  new  wnshtub,  can  l)e  used  for  mixing,  hut  not  for  storing  the  electrolyte. 
1'lie  electrolyte  must  be  cool  when  ])oured  into  the  cells. 

Note. — For  type  D  cells  (fid!  numlier  of  plates  installed),  when  being  first  put 
into  conmu.ssion,  electrolyte  of  I.ISO  si)ecific  gravity  or  22°  Baume  must  be  \ised. 
If  the  electrolyte  is  to  be  mixed  on  the  ground,  the  proportions  of  acid  (of  1.S40 
.«;pecific  gravity)  and  water  an?  one  part  acid  to  five  and  one-quarter  of  water, 
by  volume.  I>in-ing  the  initial  charge  the  gravity  will  rise  to  about  1.210  (the 
slanrliird  gravity).  For  type  D  cells  (less  than  full  number  of  i)lates  installed) 
electrolyte  of  1.210  specilic  gravity  sliould  l)e  iised. 

LOCATION    OF    IJATTERY. 

0.  The  proper  lociilion  is  inqxirtant.  It  should  preferably  be  in  a  separate 
room,  which  should  be  well   venlihitcd,  dry,  ;ind  of  niodci-iit(>  tt'mi)ei\Mtur<\ 

7.  The  ventilation  should  be  free,  not  only  to  insure  dryness  (in  a  damp 
rooiri  leakage  from  grounding  is  li;dtle  to  develoj),  but  to  i)reveid  chance  of  an 
exitlosion,  as  the  ga.ses  given  off  dui'ing  charge  form  an  exitlosive  mixture  if 
(•(infilled.  F''or  this  reason  never  bring  an  ex]tose(l  flame  near  the  battery  when 
it  is  gassing. 

(18) 


Voltaic  Cell,  Ohm's  Law,  Batteries — Chapter   1 .  19 

8.  To  obtain  the  best  results,  the  room  temperature  should  be  between  50° 
and  80°  F.  If  the  temperature  is  very  high,  that  is,  over  80°  F.,  for  any  great 
length  of  time,  tlic  wear  on  tiic  philcs  is  excessive.  If  tlie  teniperature  is  low, 
no  harm  results,  but  tiie  availai)ie  capaeity  is  reduced  during  the  period  of  low 
temperature. 

INSTALLING   BATTEKY. 

9.  Before  assembling  the  cells,  suitable  racks  or  stands  should  be  provided 
and  so  located  in  the  room  that  each  cell  will  be  easily  accessible. 

10.  Place  the  jars  in  the  trays,  which  should  previously  be  filled  evenly  with 
the  top  with  tine  dry  bar  sand.  Place  the  elements  as  they  come  from  the  pack- 
ing cases  on  a  convenient  stand  or  table  (the  elements  are  packed  positive  and 
negative  groups  together,  the  positive  group  having  plates  of  a  brownish  color 
and  the  negative  of  a  light  gray;  also  the  negative  group  always  has  one  more 
plate  than  tlie  positive  grouji).  Scrape  both  sid(>s  of  the  lug  at  the  bolt  hole 
to  in.sure  good  contact  when  the  cells  are  connected  together.  Cut  the  binding 
strings  an<l  carefully  pull  the  positive  and  negative  groups  apart.  Remove 
any  loose  or  foreign  matter  and  place  the  negative  group  crosswise  on  a  strip 
of  webbing;  then  slip  the  plates  of  the  positive  group  between  tliose  of  the 
negative  group,  so  that  the  vertical  edges  of  all  the  plates  will  be  flush.  (See 
fig.  l-I). )  The  spacing  sticks  should  then  be  inserted,  as  shown  in  figure  1-D, 
in  order  to  keep  the  plates  apart  while  lifting. 

11.  Lift  the  element  by  the  webbing  and  lower  very  cai'efully  into  the  jar 
(fig.  1-E),  withdrawing  the  webbing  and  spacing  sticks  when  the  element  is 
properly  in  i)lace.  Be  sure  that  the  hanging  lugs  rest  evenly  on  the  sides  of 
the  jar.  Lift  the  cell,  together  with  the  sanil  tray,  into  position  on  the  rack, 
leaving  an  air  gap  of  one-half  inch  between  trays.  Be  careful  that  the  direc- 
tion of  the  lugs  is  relatively  the  same  in  each  case,  thus  bringing  the  positive 
lug  and  the  negative  lug  of  adjacent  cells  together.  This  insures  the  proper 
polarity  throughout  the  battery,  bringing  a  i)ositive  lug  at  one  free  end  and  a 
negative  at  the  other.  If  cells  are  connec-ted  with  wrong  polarity,  the  plates 
will  be  seriously  injured.  If  wood  sand  trays  (fig.  1-F)  are  used,  put  the 
gla.ss  insulators  in  place  by  first  raising  one  end  of  the  tray  and  then  the 
other  end,  the  insulators  being  so  located  under  the  tray  that  they  will  be 
directly  luider  the  corners  of  the  jar.  Glass  sand  trays  (fig.  1-E)  have  pro- 
jections, or  feet,  on  the  bottom,  and  therefore  do  not  recpiire  insulators. 

12.  When  all  the  cells  are  in  position  bolt  the  lugs  together,  first  applying 
vaseline  or  grease  to  the  bolt  studs.  The  nuts  should  be  gone  over  and 
tightened  several  times  after  the  lugs  are  first  fastened  together,  to  insure 
thoroughly  good  connection.  At  this  time  the  connections  with  the  charging 
source  (which  must  be  available  for  charging)  nnist  be  made  ready. 

13.  The  wood  separntors  can  now  be  installed.  Itemove  from  packing  case  or 
water  bath  only  suflicieut  sheets  and  dowels  for  e(piipi)ing  a  f(>w  cells  at  a  time. 
The  dowels  nnist  always  be  placed  on  the  sheets  at  right  angles  with — that  is, 
across — the  grain  of  the  wood.  The  separators,  when  eipiiiiped  with  the  dowels, 
should  be  inserted  from  the  top  (see  fig.  1-F),  one  between  each  plate  of  the 
element,  the  long,  solid  pointed  end  of  the  dowels  in  every  case  being  downward. 
Immediately  after  an  element  has  been  equipped  with  its  sejiarators  the  cells 
should  be  filled  with  electrolyte  to  one-half  to  three-quarters  inch  above  tiiQ 
top  of  the  plates.  An  element  with  the  separators  in  place  must  not  be  ex- 
posed to  the  air  any  longer  than  is  absolutely  necessary.  When  the  electrolyte 
is  in  all  the  cells,  place  the  glass  hold-downis  in  position  on  the  separators, 
across  the  miihlle  of  the  cell,  and  at  right  angles  with  the  plates. 

CONNKCTING    VP   THE   CIIAKGING    CIRCTIT. 

14.  Direct  current  only  must  be  used  for  charging.  If  alternating  current 
alone  is  availaltle,  a  current  rectifier  must  be  used  for  obtaining  direct  current. 
In  connecting  the  battery  for  charging,  the  positive  pole  of  the  charging  source 
must  be  connected  to  the  positive  end  of  the  battery,  and  likewise  the  negative 
of  the  charging  source  to  the  negative  of  the  liattery.  If  a  voltmeter  is  not  at 
hand,  the  polarity  may  be  determined  by  dipping  two  wires  from  the  charging 
terminal  into  a  glass  of  water  to  which  a  teasjioonfid  of  table  salt  has  been 
added,  care  being  taken  to  keep  the  ends  at  least  1  inch  apart  to  avoid  danger 
of  short  circuits.     Fine  bubbles  of  gas  will  be  given  off  from  the  negative  pole. 

(19) 


20 


Signal  Corps  Manual  No.  3. — Chapter  1, 


Hard  Rubber  Pin  to 
support  Separator 


Hard  Rubber  Pin  to 
support  Separator 


1 

r 


Fig.   1-A. 
Assembly  of  Typo  F  separator. 
(See  par.  13.) 


Fig.   1-B. 

Jliddle  dowel 

(sliowiiiiT 
support  pm). 


A-> 


-VssemMy  oi  Typo  D  and  K  sepa- 
rators. 
(See  par.  13.) 


Fig.  1-D.  Fig.   1-E.  Fig.  1-F. 

(See  par.  10.)  (Sec  par.  11.)  (Sco  pars.  U  and  i;i.) 

ASSEMBLY   OF   STORAGE    BATTERY    PARTS. 

'J'dlilc  of  Vdlinns. 


Tvpe 

D. 

r 

T 

Size  of  plates  (not  including  lups). 

3 

31 

12 

6  by  C  inches. 

73  by  75  inches. 

11  by  lOJ  inches. 

5 

5 

7 

18 

7 

lOi 
25 

9 

10 
14 

20 

11 

12.i 
17.1 

30 

13 

15 
21 

25 

5 

10 
14 

22 

7 

15 
21 

30 

9 

20 
28 

33 

11 

25 
35 

37 

13 

30 
42 

40 

15 

35 
49 

42 

9 

40 
5li 

30 

11 

50 
70 

32 

13 

00 
81 

42 

15 

Normal  rate  (amperes),  clmrse 
and  disi^liarce 

Ma.NJmum  cliarKe  rale  (amperes). 

Huii^'o  in  specific  pravitv  fapprox- 
imal  c)  for  complete  cliscliar«e  ' . 

70 
98 

45 

'  For  exa 
discharged 
gravity. 


mplo:  If  the  specifie  gravity  of  a  tvt)0  K7  cell  is  1 .207  wlion  fully  charged,  it  will  bo  completely 
when  the  gravity  lias  fallen  about  30  points  (0.030  specific  gravity),  i.  o.,  to  about  1.177  specific 


(20) 


Voltaic  Cell,  Ohm's  Law,  Batteries— Chapter   1.  21 

INITIAL   CHARGE. 

[See  table  of  rating.] 

16.  The  charge  should  be  started  at  tlie  normal  rate  as  soon  as  practicable 
after  all  the  cell.s  are  filled  with  electi'olyte  and  all  the  connections  made,  and 
continued  at  the  same  rate  until  both  the  si)ecific  gravity  and  voltage  show  no 
rise  over  period  of  10  hours,  and  gas  is  being  freely  given  off  from  all  the 
plates.  The  positive  plates  will  gas  sometimes  before  the  negative  plates.  To 
meet  these  conditions,  from  50  to  CO  hours'  charging  at  the  normal  rate  will  be 
reciuired  ;  if  the  rate  is  k'ss,  the  time  rcMiuired  will  be  proportionately  increased. 
In  case  the  charge  is  intiTi-upted,  jiarticulariy  during  its  earlier  stages,  or  if  it 
is  not  started  as  soon  as  the  electrolyte  is  in  the  cells,  the  total  charge  requireil 
(in  ampere  hours)  will  be  greater  than  if  the  charge  is  continuous  and  started 
at  once.  As  a  guide  in  following  the  progress  of  the  charge,  readings  of  the 
cuiTent,  specihc  gravity,  and  voltage  .should  l>e  regularly  taken  and  recorded. 
The  gassing  should  also  be  watched,  and  if  any  cells  are  not  gassing,  or  are 
not  gassing  as  much  as  the  surrounding  cells,  they  should  be  carefully  examined 
a  nil  the  cause  of  the  trouble  removed.  The  temperatiu'e  of  the  electrolyte 
should  be  closely  watched,  and  if  it  approaches  100°  F.  the  charging  rate  must 
be  reduced,  or  the  charge  temporarily  stojiped  until  the  temi)erature  lowers. 
The  .specilic  gravity  will  fall  after  the  electrolyte  is  added  to  the  cell  and  will 
then  greatly  rise  as  the  charge  progresses  until  it  is  up  to  the  1.210  or  there- 
about. The  voltage  of  each  cell  at  the  end  of  charge  will  be  between  2.50  and 
2.70  volts,  and  for  this  reason  a  fixed  or  definite  voltage  should  not  be  aimed 
for.  If  the  specific  gravity  of  any  of  the  cells  at  the  completion  of  the  charge 
is  below  1.205,  or  above  1.215,  allowance  being  nuule  fV)r  the  temperature  cor- 
rections (see  below),  it  should  be  adjusted  to  within  these  limits,  adding  elec- 
trolyte if  low,  and  replacing  some  of  the  electrolyte  in  the  cell  with  water  if 
high,  keeping  the  surface  at  the  proper  height  (one-half  to  three-foiu'tlis  inch) 
above  the  to])  of  the  ])lates. 

TEMPEBATURE. 

17.  As  the  temperature  affects  the  gravity,  this  nuist  be  considered  and  cor- 
rections made  as  follows:  To  correct  to  normal  temperature  (70°  F. )  subtract 
one  point  (0.001  specilic  gravity)  for  each  8°  F.  below  70°  and  add  one  point 
for  each  o°  F.  above  70°.  For  instance,  electrolyte,  which  is  1.213  at  Gl°  and 
1.207  at  79°,  will  be  1.210  at  70°,  It  is  of  the  utmost  importance  that  the  initial 
charge  be  (ompleted  in  every  respect.  If  there  is  any  doubt,  it  is  better  to 
(•barge  too  long  than  risk  injury  to  plates  by  stopping  the  initial  charge  before 
it  is  complete. 

Whi](>  the  preceding  directions  may  be  applied  to  any  make  of  storage  bat- 
tery, different  manufacturers  recommend  slightly  ditferent  methods  of  pro- 
cedure in  the  initial  charge  of  their  batteries,  which  should  be  carefully  fol- 
lowed, as  this  is  ,the  only  means  by  whii-h  they  can  be  held  responsible  for 
the  conduct  of  their  cells,  which  may  be  sold  on  guaranties. 

INITIAL    CHARGES    FOR    DIFFERENT    ilAKES    OF    CELLS. 

For  a  "  chloride "  battery  the  charge  should  be  started  at  the  normal  rate 
as  soon  as  the  electrolyte  is  in  the  cells  (covering  the  plates  about  three-fourths 
inch),  and  continued  at  the  same  rate  until  both  the  specific  gravity  and 
voltage  show  no  rise  over  a  period  of  10  hours  and  all  the  plates  are  gassing 
freely.  Electrolyte  of  1.170  specific  gravity  is  furnished  for  the  type  BT,  CT, 
PT,  and  D  cells  and  of.  1.210  specific  gravity  for  all  the  other  larger  types. 
The  positive  plates  will  gas  some  time  before  the  negatives.  To  meet  these 
conditions,  from  50  to  60,  hours  continuous  charging  at  the  normal  rate  will 
be  required  for  the  larger  cells,  while  the  types  BT,  CT,  PT,  and  P3T  require 
from  30  to  40  hours  for  the  initial  charge;  and  if  the  rate  is  less,  the  time 
required  will  be  proportionately  increased.     In  case  the  charge  is  interrupted, 

(21) 


22 


Signal  Corps  Manual  No.  3. — Chapter  1. 


particularly  during  its  earlier  stages,  or  if  it  is  not  started  as  soon  as  the 
electrolyte  is  in  the  cells,  the  total  charge  requiriMl  (in  ampere  hours)  will  be 
greater  than  if  the  charge  is  continuous  and  started  at  once. 

For  this  operation  the  Willard  Storage  Battery  Co.  rccoiumends  as  follows: 

The  charge  must  be  commenced  immediately  upon  filling  the  cells  with  elec- 
trolyte of  1.200  specific  gravity.  The  battery  sliould  be  charged  at  a  rate  equal 
to  two-thirds  of  its  normal  or  eight-hour  charging  rate.     The  charging  should 


Fig.    1    10.— BATTERY,    STORAGE,   CHLORIDE. 


be  continued  until  llic  voltage  of  each  cell  is  2.(1  volts,  the  reading  IxMUg  tak(Mi 
while  the  iiattcry  is  being  charged  at  the  above  rate.  After  the  cells  have 
reached  the  voltage  named  above,  or  higher,  the  charge  sliould  be  continued 
until  tiie  specific  gravity  of  each  cell  ceases  to  rise,  or  has  remained  constant 
for  at  least  throe  hoiii-s.  This  will  usually  happen  after  a  battery  has  lu^en 
charged  f<»r  a]ii»roximalely  (iO  hours.  The  experience  of  the  Signal  Corps 
has  i)een  that  a  longer  juriod  of  charge  is  re<|uired.  If  any  cells  do  not  show 
the  proper  rise  in  voltage,  or  do  not  gas  freely,  they  should  be  examined.  Care 
should  be  taken  that  there  are  no  internal  short  circuits.  If  there  are  they 
should  be  removed  at  once  and  the  chai'ge  continued  until  the  cells  indicate 
us  above. 

(22) 


Voltaic  Cell,  Ohm's  Law,  Batteries — Chapter   1 


23 


The  Gould  Storage  Battfi-y  Co.  reconiineiuls  tlie  I'ollowiiij:  proctMlure  for  the 
initial  charge  of  their  batteries : 

Fill  the  cells  with  the  electrolyte  furiiished  which  lias  a  specilie  gi'avity  of 
1.210.  Conuiience  initial  charge  at  twice  the  normal  or  eight-liour  rate  and  con- 
tinue for  12  hours,  then  reduce  to  1.4  times  the  normal  charge  rate  for  2(i 
hours,  then  decrease  to  the  normal  or  eight-hour  rate  and  charge  for  20  hours. 
The  specific  gravity  should  he  about  1.210  (corrected  to  temperature)  at  the 
end  of  cliai"ire. 


Fig.    1-11.— BATTERY,    STORAGE,    WILLARD. 

In  later  paragraphs  on  the  maintenance  of  storage  batteries  emphasis  is  laid 
<tn  the  fact  that  storage  batteries  should  not  be  allowed  to  remain  in  a  dis- 
cliarged  state.  This  is  because  lead  oxide  immersed  in  sulphuric  acid  will  be 
chemically  attacked,  independent  of  any  current  tlow,  and  change  into  lead 
sulphate,  so  that  discharged  plates  tend  to  take  on  a  coating  of  lead  sulphate, 
a  nonconductor,  impairing  the  efficiency  of  the  cell  as  an  accumulator. 


(23) 


24 


Signal  Corps  Manual  No.  3. — Chapter  I. 


Various  methods  of  manufacture  are  used  to  give  tlie  plates  more  current 
capacity — that  is,  to  expose  more  reducible  peroxide  of  lead  in  the  positive  and 
spongy  lead  in  the  negative  plate  to  the  action  of  the  electrolyte.  The  various 
methods  (jf  manufacture  consist  in  changing  the  form  of  the  grids  and  different 
methoils  of  filling  them  Avith  the  oxides  and  spongy  pure  lead.  Inasmuch  as 
neither  of  these  have  any  mechanical  strength  in  themselves,  the  grids  or 
frames  are  necessary  to  make  up  a  suitable  electrode. 


<;lass  covku 


^l.l^M;A•ro(;  i;i;t.\i\i:k 


^-.«> 


noi.T 

CON'XECTOIl 


WOOlj   Si;i'\i;  \T.  I 


M:(;.\ri\K  uijui  r 


(•()\KR 


I'asiTivL;  (iijoi  !• 


(iLASS    JAR 

OAK    S\NI)    TUAY.WI'IH    SAM) 

(il,  \SS    INSULA  roij.s 


» 


ri^;.    1-12.  — BATTERY,    STORAGE,   GOULU. 
(24) 


Voltaic  Cell,  Ohm's  Law,  Batteries —  Chapter   1 


25 


Different  makes  of  .*;torajit'  l)atteries  are  used  by  tlie  Signal  Corps.  l)ut  to 
date  practically  all  tliose  used  are  of  the  lead  types,  made  by  the  Electric 
Storage  Battery  Co.,  known  as  the  "  Chloride "  battery ;  those  made  by  the 
Willard  Storage  Battery  Co.  and  known  as  the  "  Willard  ;  "  and  those  made 
by  the  Gould  Storage  Battery  Co.,  known  as  the  "Gould"  batteries.  (See 
tigs.  1-10,  1-11,  1-12.) 

TABLE  OF   RATINGS. 

The  ampere-hovir  capacity  and  sizes  of  batteries  can  be  determined  by  the 
table  herewith,  covering  all  the  makes  and  types  of  storage  batteries  used  by 
the  Signal  Corps. 

To  determine  the  normal  charge  and  discharge  rates  of  a  battery  multiply  the 
"  amperes  per  positive  plate  "  for  the  particular  type  in  question  by  the  number 
of  positive  i)lates  i)er  cell ;  thus  for  a  type  F  battery  of  13  plates  per  cell  (6  posi- 
tive and  7  negatives)  the  normal  rate  is  60  amperes. 


Type  and  number  of  plates. 

Size  of  plates,  not  including  lugs. 

Normal 
charge  rate 
(S  hours) 
per  posi- 
tive plate. 

Gould. 

Chloride. 

Willard. 

Manufac- 
turers 
type. 

Number 
of  plates. 

Manufac- 
turers 
type. 

Number 
of  plates. 

Manufac- 
turers 
type. 

Num- 
ber of 
plates. 

3  bv  4  inches       

Amperes. 

1^ 
li 
li 
2' 
2* 
3' 
4i 

GGW... 

CW 

CL 

2 
3 
3 

BT 

2 

CC 

2 

1 

5  bv  5  inches       

CT 

2 

DC 

2 

CX 

CM 

CY 

3 
3 
3 

6  bv  6  inches                 .      .  . 

D 

PT 

ET 

}^ 

3-13 
2 
2 

5-15 

5  bv  8J  inches 

BC 

EC 

E 

2 

2 

7 J  bv  ~l  inches 

JCN i              3 

\N' 5-15 

CZ !               3 

0 5-13 

5-15 

8  bv  9  inclies 

6 
10 
10 

10'.  bv  lOV  inches          .  .  . 

10*  by  11  inches    

F 

9-27 

F. ...... 

^27 

In  all  of  the  above  types,  except  the  two-plate  type,  there  is  one  more  negative  than 
positive  plate.     All  two-plate  types  have  one  negative  and  one  positive  plate. 

ADUITIONAl,   l.XSTKUCTIONS    FOR    ERECTING    STORAGE    B.\TTERIES. 

Storage  batteries,  wlien  received  at  storerooms,  should  be  placed  in  a  dry 
location  and  an  effort  made  to  erect  the  batteries  as  .soon  as  po.ssible  after 
their  receipt.  When  unpacked,  preparations  should  be  made  to  handle  each 
group  of  elements  as  a  unit.  After  the  lead  elements  are  unpacketl.  care 
must  be  used  in  handling  so  that  the  plates  and  lugs  will  not  be  bent  or 
broken.  This  can  be  accomplished  by  lifting  the  plates  with  a  stick  placed 
under  all  the  lugs  of  each  element,  which  can  then  be  lowered  carefully  in 
the  jars.  Care  must  be  used  to  prevent  breaking  the  tank  or  jar,  or  bending 
the  plates  of  supporting  lugs.  Types  of  storage  battery  racks  suitalilp  for 
cells  of  the  sizes  installed  by  the  Signal  Corps  are  shown  in  figures  1-13  and 
1-14.  These  can  be  made  of  any  sound  timber  with  the  necessary  strength, 
which  can  be  secured  locally;  all  boltheads  carefully  puttied  over,  the  whole 
given  several  coats  of  acid-proof  paint.  The  rack  is  then  located  in  its 
permanent  position,  and  if  the  battery  room  has  an  asphalt  floor,  provision  is 
made  for  wide  bases  for  the  uprights  of  the  rack  to  prevent  them  sinking 


(25) 


26 


Signal  Corps  Manual  No.  3. — Chapter  1 


into  the  floor.  The  rack  .shouUl  he  carefully  leveled  before  the  batteries  are 
installed.  The  stringers  must  be  of  sufficient  strength  to  support  the  cells 
rigidly  and  perfectly  level.  The  insulators  should  be  placed,  and  the  wood 
tanks  or  sand  trays  and  glass  jars  carefully  aligned,  care  being  taken  that 
they  do  not  touch  each  other.  If  bolt  connections  are  nsed,  they  should  be 
thoroughly  cleaned  by  scraping.  The  strap  lugs  should  also  be  scraped  where 
they  will  be  in  contact,  and  all  connections  bolted  tight  and  then  painted  with 
an  insulating  paint.  The  leads  to  the  storage  battery  from  the  switchboard 
room  should  be  lead-covered  cable  if  possible.  The  sheath  should  be  cut  back 
about  S  inches  from  the  end.  The  terminal  lugs  should  then  be  sweated  onto 
the  end  of  the  conductor  by  filling  the  hole  in  the  terminal  lug  with  melted 
resin  solder,  into  which  the  wire  is  forced  after  being  carefully  cleaned  and 
tinned.  The  insulation  and  the  shank  of  the  lug  is  then  carefully  taped  up 
and  given  several  coats  of  acid-proof  paint.  Where  the  lead  rises  from  the 
floor,  loricated  conduit  can  be  used  to  protect  it  from  injury. 

The  sand  trays  and  sand  must  be  carefully  dried  before  being  installed.  The 
trays  can  be  dried  by  ordinary  methods,  but  the  sand  must  be  baked  for  a 
sufficient  time  to  insure  that  all  moisture  has  been  expelled.  Before  com- 
mencing the  intitial  filling  of  the  jars  with  electrolyte,  if  wood  separators  are 


5 


CrtfcVr  zurfact  given  bvo  good  coats  of  aad-proof paint 


Hv  r"^1 


r^'i 


'i'dc^yeJ  qfuui and naitta 


Fig.    1-13.— BATTERY,    STORAGE,   TELEPHONE,    STAND    FOR. 

used,  they  should  be  installed  and  arrangements  should  be  made  to  do  the 
work  rapidly.  A  su(fi(ient  number  of  glass  or  earthenware  jars  nuist  be  avail- 
able so  that  several  men  can  be  engaged  in  the  filling  of  the  l)attery  jars  with 
electrolyte.  It  is  essential  tlml  tlic  electrojyte  l)e  kept  clean  during  this 
process,  and  every  precaution  should  be  taken  to  that  end.  Electrolyte  of  the 
proper  specific  gravity  is  furnished  with  each  battery  by  the  maker.  Care 
should  be  taken  that  a  sufi'icient  amount  of  electrolyte  of  the  correct  specific 
gravity  is  available  before  the  filling  is  connni'uced.  It  should  be  known  with 
ab.solute  certainty  that  the  reciuired  i)o\ver  for  the  necessary  length  of  time 
will  !)(>  availaitle  before  an  initial  charge  is  conuuenced.  The  maxinnim  voltage 
availaltle  for  <liarging  should  be  at  least  2.7.")  volts  for  every  cell  to  b(?  charged, 
and  till"  ami»eragc  available  lliat  recpiired  by  the  tyi»e  of  cell. 

CAliK    Ol'    STOIt.\(lK    li.MTKKIKS. 

Kxcessive  charging  nnist  be  avoided.  A  battery  should  not  be  under- 
charged, overdiscliarged,  or   let    to  stand  completely  discharged. 

I')attery  slionlil  prefcraljly  be  charged  at  the  normal  rate.  It  is  iiiii)ortant 
tliat  it  should  he  sullicicnl  ly  charged,  but  the  charge  should  not  be  <(>ntinued 
beyond  that  jioint.  I'.olli  from  the  standi)oint  of  efficiency  and  lil\'  of  the 
plates  the  best  practice  is  tlie  method  which  embraces  what  may  be  called  a 


(20) 


Voltaic  Cell,  Ohm's  Law,  Batteries — Chapter   1 


27 


<cDOQiiJiLOi:4t>^Jj2ZOQ-OZQ: 


46581°— 17 3 


28 


Signal  Corps  Manual  No.  3. — Chapter  1. 


regular  charge,  to  be  given  when  battery  is  from  one-half  to  two-thirds  rlis- 
fhargetl,  and  an  overcharge  to  be  given  once  every  week. 

A  "  pilot  cell "  should  be  selected,  one  that  is  readily  accessible,  and  at  the 
same  time  representative  of  the  battery  as  a  whole.  The  surface  of  the 
electrolyte  in  this  cell  must  be  kept  at  a  fixed  height,  three-fourths  inch  above 
the  top  of  the  plates,  by  adding  a  small  quantity  of  water  occasionally.  This 
cell  is  to  be  used  particularly  in  following  the  charge  and  indicating  when  it 
should  be  stopped.  Where  batteries  are  not  equipped  with  the  full  number  of 
plates,  the  excess  electrolyte  in  the  pilot  cell  should  be  displaced  by  a  properly 
treated  and  weighted  wooden  block. 

REOfLAR     CIIAROE. 

The  normal  rate  should  bo  used  throughout  the  charge  when  conditions 
pei'mit ;  but  if  it  is  necessary  to  hasten  the  charge  a  maximum  charging  rate 
as  given  in  the  table  which  follows  may  be  used  during  the  first  part  of  the 
charge ;  that  is,  until  the  cells  begin  to  gas,  when  it  should  be  reduced  to 
normal.  Do  not  charge  at  a  higher  rate  than  normal  after  the  cells  are  gassing. 
The  indications  of  sufficient  charge  are  as  follows : 

(a)  The  gravity  of  the  pilot  cell  having  risen  to  a  point  which  is  five  points 
(0.005  specific  gravity)  below  the  maximum  reached  on  the  preceding  over- 
charge ;  for  instance,  if  the  maximum  reached  on  the  preceding  overcharge 
was  1.209,  the  gravity  to  be  reached  on  the  regular  charge  is  1.204.  If  the 
cells  are  but  partially  filled  with  plates  and  the  excess  electrolyte  is  not  dis- 
placed, the  limit  should  be  three  points  (0.003  specific  gravity)  instead  of  five 
points    (0.005  specific  gravity). 


Type. 


Size  of  plates  (not  including  lugs). 


6  by  6  inches. 


73  by  7J  inches. 


11  by  lOJ  inches. 


Number  of  plates  per  cell 

Normal  rate  (amperes)  charge 
and  dischargp 

Maximum  charge  rate  (amperes) . . 

Range  in  specific  gravity  (ap- 
proximate) for  complete  dis- 
charge ' 


3 

5 

7 

9 

11  13  i  5 

7 

9 

11 

13 

15 

9 

11 

13 

2.J 
3A 

5 
7 

7J 
lOi 

10 
14 

12h    15-  10 
17i  21  14 

15 
21 

20 

28 

25 
35 

30 

42 

35 

49 

40 

56 

50 
70 

60 
84 

12 

IS 

25 

20 

30  !  25  22 

1 

30 

33 

37 

40 

42  30 

32 

42 

15 


•  For  examj)!)*:  If  1  tie  specific  gravity  of  a  type  E-7  coll  is  1.207  when  fully  charged,  it  will  be  completely 
discharged  when  the  gravity  has  fallen  about  ;iOpoinls  (0.030  sp.  gr.),  i.  e.,  toal)out  1.177  specific  gravity 

(h)  The  voltage  across  battei-y  having  risen  to  a  point  which  is  0.05  to  0.10 
volt  per  cell  below  what  it  was  on  the  preceding  overcharge,  the  charging 
rale  being  I  he  same  in  both  cases;  for  instanct*.  if  the  maxinunn  voltage  it«>r 
(I'll  ;illain(«d  on  the  overcharge  is  2.52.  the  voltage  per  cell  to  be  reached  on 
the  regular  charge  is  from  2.12  to  2.17  volts  pin-  cell. 

(c)   The  cells  all  gassing  moderately. 

OVKRCMARCK. 

Once  ;i  wi'fU.  and  preferably  on  the  same  day  of  the  weel<,  tli(>  regular  charge 
shoidd  be  |)roloi)ge(l  until  the;  conditions  given  below  an^  fulfilled: 

If  rate  is  less  than  normal,  the  lime  at  maxinnnn  imist  be  projMii-t  ionately 
increased. 

(«)  The  gravity  of  the  jiijot  cell  luiving  reached  ii  maximum,  five  successive 
J5-minute  readings  of  this  ceil  showing  no  fmiher  rise. 


(28) 


Voltaic  Cell,  Ohm's  Law,  Batteries — Chapter   1 .  29 

(&)  The  voltage  aci-oss  battery  luivinj,'  reached  a  maximum,  five  successive 
15-minute  readings  showing  no  furtlier  rise,  tlie  cluirging  rate  being  kept 
constant. 

(c)  The  cells  all  gassing  freely. 

As  the  temperature  affects  tiie  gravity,  this  must  be  considered  and  correc- 
tion made  as  follows:  To  correct  to  normal  temiierature  (70°  F.).  .subtract  one 
point  (0.001  specific  gravity)  for  each  3°  F.  below  70°  and  add  one  point  for 
each  3°  F.  above  70°.  For  instance,  electrolyte,  which  is  l.lil3  at  01°  and  1.207 
at  79°,  will  be  1.210  at  70°. 

CiENERAL. 

After  the  completion  .of  a  charge  and  the  current  off.  the  voltage  will  quite 
rapidly  fall  to  about  2.0.5  volts  per  cell  and  there  remain  while  <in  open  circuit; 
falling  to  2  volts  when  the  disl-harge  is  .started. 

Also,  after  the  completion  of  a  charge,  particularly  an  overcharge,  the  .specific 
gravity  of  the  electrolyte  will  rise  slightly,  due  to  passing  off  of  the  gas  bubbles 
formed  during  the  charge.  For  this  reason  ail  of  the  pilot-cell  gravity  readings 
must  be  taken  before  the  charging  current  is  cut  off. 

The  voltage  should  not  be  allowed  to  fall  below  1.75  volts  per  cell  with  cur- 
rent at  normal  rate;  the  limiting  voltage,  however,  is  higher  if  the  rate  is  less 
than  normal,  and  lower  if  the  rate  is  above  normal. 

The  specific  gravity  falls  very  closely  in  direct  proportion  to  the  ampere 
hours  discharged  and  can  therefore  be  used  as  a  guide  in  following  the  dis- 
charge; thus,  with  the  cells  equipped  with  the  full  number  of  plates  or  the 
pilot  cell  with  a  displacing  block,  the  range  in  gravity  from  full  charge  to 
complete  discharge  is  as  given  in  the  preceding  table.  If  the  cells  have  not  the 
full  number  of  plates  and  therefore  have  an  excess  of  electrolyte,  the  range  is 
proportionately  decreased,  as  is  also  the  case  where  the  capacity  of  the  battery 
has  decreased  due  to  normal  wear  or' to  abuse.  If  the  discharge  is  at  higher 
l-ates  than  normal,  the  gravity  range  is  reduced  in  proportion  to  the  reduced 
atupere  hour  capacity  at  the  higher  rates. 

The  gravity  and  voltage  limits  are  not  necessarily  reached  at  the  same  time ; 
but  either  being  reached,  the  discharge  should  be  stopped. 

The  specific  gravity  of  the  pilot  cell  (or  tjie  battery  voltage  and  current  if 
the  pilot-cell  method  is  not  used)  should  be  rea<l  and  recorded  just  before  the 
beginning  and  end  of  every  charge ;  also  the  temperature  of  the  pilot  cell  at  the 
end  of  charge. 

A  specific-gravity  reading  of  all  cells  should  be  taken  and  recorded  once  a 
week,  just  before  the  start  of  charge  on  overcharge  day  and  also,  if  the  battery 
is  not  overcharged  weekly,  at  the  corresponding  time  on  the  off  w«'ek.  If  not 
practicable  to  take  these  readings  on  overcharge  day.  they  may  be  taken  the 
day  before.  In(livi<lual  cell  voltage  readings  are  to  be  taken  just  before  end  of 
overcharge  with  current  flowing  at  normal  rate.  Open-circuit  voltage  readings 
are  of  no  value. 

Just  before  the  overcharge  every  cell  should  be  inspected  carefully,  paying 
especial  attention  to  any  cells  noted  as  loir  in  the  weekly  readings.  Make  sure 
that  the  hanging  lugs  are  in  place  and  not  touching  adjoining  lugs;  al.so  any 
peculiarity  in  the  color  of  the  plates  slumld  be  noted.  Near  the  end  of  the  over- 
charge all  cells  should  be  looked  over  to  see  that  they  are  gassing  freely. 

In  case  a  cell  falls  off  in  specific  gravity  or  in  voltage  relative  to  the  rest  of 
the  cells,  or  shows  lack  or  deficiency  of  gassing  on  overcharge  as  compared  with 
surrounding  cells,  or  shows  the  color  of  the  plates  marke<lly  lighter  or  darker 
.than  the  surrouudiug  cells,  the  cause  should  at  once  be  determined  uud  remov^U. 

(29) 


30  Signal  Corps  Manual  No.  3. — Chapter  1. 

Short'  circuits  are  to  be  removed  witli  :i  thiu  strip  of  liard  wood ;  never  use 
metal. 

If,  after  the  cause  of  the  trouble  has  been  removed,  the  readinj^s  do  not 
come  up  at  the  end  of  the  overcharge,  then  the  cell  must  be  cut  out  of  circuit 
on  the  discharge,  to  be  cut  in  again  just  before  beginning  the  next  charge.  If 
this  does  not  bring  it  up,  the  process  should  be  repeated. 

Impurities  in  the  electrolyte  will  also  cause  a  cell  to  work  irregularly.  Should 
it  be  known  that  any  impurity  has  gotten  into  a  cell,  it  should  be  removed  at 
once.  In  case  removal  is  delayed  and  any  considerable  amount  of  foreign 
matter  becomes  dissolved  in  the  electrolyte,  this  solution  should  be  replaced 
with  new  immediately,  thoroughly  flushing  the  cell  with  water  before  putting 
in  the  new  electrolyte.  If  in  doubt  as  to  whether  the  electrolyte  contains 
impurities,  a  half-pint  sample,  taken  at  the  end  of  discharge,  should  be  sub- 
mitted to  the  department  signal  officer  for  test.    ' 

The  accumulation  of  sediment  in  the  bottom  of  the  jars  must  be  watched  and 
not  allowed  to  touch  the  plates,  as  if  this  occurs  rapid  deterioration  will  result. 
To  remove  the  sediment  from  type  D  and  E  cells,  first  prepare  in  a  suitable 
receptacle,  such  as  a  glass,  earthenware,  or  lead-lined  tank,  enough  new  elec- 
trolyte of  1.210  specific  gravity  to  fill  several  cells.  Starting  at  one  end  of  the 
battery,  remove  several  elements,  pressing  the  plates  together  to  avoid  disturb- 
ing the  separators;  siphon  or  pour  off  the  electrolyte,  taking  care  to  disturb 
the  sediment  as  little  as  possible ;  clean  the  jars,  examine  element  for  dam- 
aged separator's,  and  replace  with  new  where  necessary ;  put  the  element  back 
and  fill  the  cells  with  the  new  electrolyte  at  once,  so  that  the  elements  will  not 
dry.  Then  add  enough  1.400  specific  gravity  acid  to  the  old  electrolyte  drawn 
from  these  cells  to  bring  it  up  to  1.210  specific  gravity,  so  that  it  can  be  used  to 
fill  the  next  two  or  three  cells  cleaned,  and  so  on  throughout  the  battery.  The 
1.400  specific  gravity  acid  must  never  be  added  directly  to  the  cells.  Before 
bolting  cells  together,  the  lugs  should  be  well  scraped  at  point  of  contact.  At 
completion  of  the  work  give  a  long  charge  until  the  gravity  and  voltage  have 
been  at  a  maximum  for  from  5  to  10  hours.  At  the  end  of  this  charge  read  the 
gravity  of  all  cells  and  adjust  where  necessary  to  normal  (1.205  to  1.215). 
Type  F  cells,  on  account  of  their  size  and  weight,  can  usually  be  best  cleaned 
by  either  the  "scoop"  or  "water  circulaticm  "'  metliods,  though  if  care  is  exer- 
cised the  sediment  can  be  removed  as  described  above. 

Note. — Very  often  it  will  be  found  that  the  depth  of  sediment  is  };r(>atest  under  the 
middle  plates,  and  if  the  sediment  is  leveled  over  the  bottom  of  the  eell  its  removal  will 
not  be  necessary  for  some  time  lonjrer.  The  leveling  can  bo  done  l).v  usini;  :ni  L-shaped 
device,  which  has  no  metal  in  lis  construction. 

Water  only  is  lost  by  evaporation  and  nuist  Ite  rephiced  with  water.  Do  not 
allow  the  surface  of  the  electrolyte  to  get  below  the  top  of  the  plates;  keep  it 
at  its  proper  level  (one-half  to  thr*ee-fourths  inch  above  the  top  of  the  phites) 
by  the  addition  of  pure  water,  which  should  be  added  at  the  beginning  of  a 
charge,  preferably  the  overcharge.  It  will  not  be  necessary  to  add  new  elec- 
trolyte, except  iit  long  intervals  or  when  removing  sediment.  To  transjiort  or 
store  the  water,  use  clean  glass  or  rub!)er  vessels.  Wooden  r-eceplacles,  if  they 
have  not  been  used  for  otlier  purposes,  may  also  be  used,  but  they  should  be 
allowed  to  stand  full  oC  water  for  a  week  before  iise.  In  case  of  doubt  as  to 
tlie  purity  of  tlic  wiitcr,  ii  quart  s.-iiiipic  sliotild  be  submitted  for  test. 

Ordinarily  it  will  not  be  iicccssaiw  to  add  new  electrolyte,  except  at  long 
intervals  (once  every  year  or  two)  or  following  removal  of  sediment.  When 
the  si)ecific  gravity  of  c<'lls  in  good  condition  at  full  charge  and  at  normal 
temperatui-e    (70°   F.)    has  fallen  to  1.190,  it  should  be  restored  to  standard 

(30) 


Voltaic  Cell,  Ohm's  Law,  Batteries — Chapter   1.  31 

(1.20.")  to  l.*_'ir»)  hy  till!  addition  of  now  electrolyte  of  1.210  specific  gravity 
instead  of  water  when  repUiciiif;  evaporation.  If  the'  overcharge  gravity  is 
considerably  l»elow  1.190,  as  is  sometimes  the  case  after  removing  sediment, 
the  cpiickest  way  to  raise  the  gravity  is  to  draw  off  the  electrolyte  from  one 
cell,  refill  it  with  electrolyte  of  1.210  specific  gravity,  and  add  siiJRcient  1.400 
specific  gravity  acid  to  that  drawn  off  from  the  first  cell  to  raise  it  to  1.210, 
then  draw  off  the  electrolyte  from  the  second  cell  and  refill  with  this  1.210  elec- 
trolyte, and  so  on  throughout  the  battery.  Never  under  any  circumstances  add 
electrolyte  of  higher  gravity  than  1.210  directly  to  the  cells. 

If  it  is  not  convenient  to  procure  the  electrolyte  already  mixed  and  ready  for 
use,  it  may  be  prepared  by  diluting  sulphuric  acid  of  1.S40  .specific  gravity  or 
G6°  Baum<5  (oil  of  vitriol),  which  has  been  made  especially  for  storage  battery 
use,  with  pure  water  (preferably  distilled)  in  the  proportion  of  one  part  acid 
to  four  and  one-third  of  water  by  volume;  1.400  specific  gravity  acid  may  be 
reduced  to  1.210  specific  gravity  by  mixing  equal  volumes  of  the  acid  and  pure 
water.  It  is  absolutely  essential  that  both  the  acid  and  water  should  be  practi- 
cally free  from  impurities,  such  as  iron,  nitric  or  hydrochloric  acid.  When 
mixing,  slowly  pour  the  acid  into  the  water  (not  the  water  into  the  acid)  and 
thoroughly  stir  with  a  wooden  paddle.  The  final  specific  gravity  must  be  read 
when  the  solution  is  cool.  A  metal  vessel  must  not  be  used  for  mixing  or 
handling  the  solution;  a  glazed  or  earthenware  crock  or  a  lead-lined  tank  is 
suitable,  or  a  wooden  vessel  which  has  not  been  used  for  any  other  purpose, 
such  as  a  new  washtub,  can  be  used  for  mixing,  but  not  for  storing,  the  electro- 
lyte.   The  electrolyte  must  be  cool  when  poured  into  the  cells. 

When  charging,  those  end  cells  which  may  have  been  successively  cut  into 
circuit  on  discharge  should  be  cut  out  again  on  the  following  charge  as  soon 
as  they  are  charged  as  shown  by  their  gassing  moderately.  The  cells  which 
were  last  cut  into  circuit  on  discharge  will,  of  course,  become  charged  before 
th(jse  that  were  first  cut  in.  All  the  end  cells,  whether  used  or  not,  should  be 
cut  Into  circuit  at  the  beginning  of  the  overcharge  and  each  cell  kept  in  circuit 
until  it  gasses  freely,  but  no  longer. 

If  the  battery  is  to  stand  idle  or  be  used  at  infrequent  intervals,  an  overcharge 
should  be  given  every  two  weeks.  Several  storage  battery  companies  have 
advised  that  during  such  a  jieriod  exercising  or  discharging  battery  through 
artificial  resistance,  which  for  years  was  the  custom,  is  unnecessary  and,  in  fact, 
is  a  wear  and  tear  on  the  battery. 

If  the  use  of  the  battery  is  to  be  entirely  discontinued  for  a  period  not  longer 
than  about  nine  months  and  it  is  not  practical  to  charge  at  least  once  a  month, 
care  should  be  taken  that  an  overcharge  is  given  just  before  the  idle  period. 
Water  should  be  added  to  the  cells  during  the  overcharge  so  that  the  gassing 
will  insure  thorough  mixing.  The  level  of  the  electrolyte  should  be  about  one- 
quarter  inch  from  the  top  of  the  jars.  After  the  overcharge  is  completed, 
remove  the  fuses  to  prevent  the  use  of  the  battery  during  the  idle  period. 
Though  not  likely,  the  level  of  the  electrolyte  may,  due  to  excessive  evaporation 
during  the  idle  period,  fall  below  the  top  of  the  plates ;  if  this  should  occur, 
add  water  to  keep  them  covered  ;  if  in  a  place  where  freezing  is  apt  to  occur. 
stir  the  electrolyte  after  adding  the  water,  as  thoroughly  mixed  electrolyte  will 
not  freeze  solid. 

If  the  battery  is  to  be  entirely  out  of  service  for  over  nine  months,  then  pro- 
ceed as  follows:  After  thoroughly  charging,  siphon  off  the  electrolyte  (which 
may  be  used  again)  into  thoroughly  cleaned  glass  rceptacles,  and  as  each  cell 
becomes  empty  inunedi;itely  fill  it  with  fresh,  pure  water.    AVhen  water  is  in  all 

(31) 


32  Signal  Corps  Manual  No.  3. — Chapter  1. 

the  cells,  allow  the  battery  to  stand  12  or  15  hours.  Remove  and  throw  away 
the  wood  separators.  Next  siphon  the  water  out  of  each  cell,  and  the  battery 
can  then  he  allowed  to  stand  indefinitely.  If  there  is  any  considerable  amount 
of  sediment  in  the  cells,  it  should  be  removed  before  it  dries. 

If  the  electrolyte  has  not  been  withdrawn,  all  that  is  necessary  to  place  bat- 
tery in  commission  is  to  add  water,  if  needed,  to  the  cells  and  give  an  over- 
charge until  the  gravity  of  the  electrolyte  has  ceased  rising  over  a  period  of  five 
hours. 

If  the  battery  has  been  standing  without  electrolyte,  proceed  as  follows : 
Equip  cells  with  new  separators  and  fill  with  either  new  electrolyte  of  1.210 
specific  gravity  or,  if  the  old  electrolyte  has  been  saved,  add  enough  new  of  1.210 
specific  gravity  to  replace  loss.  Charge  for  3u  hours  at  the  normal  rate,  or  for 
a  proportionately  longer  time  at  a  lower  rate.  If  the  gravity  after  the  first 
charge  is  low,  it  should  be  restored  to  standard. 


(32, 


Chapter  2. 
TELEGRAPHY  AND   THE   INDUCTION   TELEGRAPH   SET. 

ThK   MoKSK  TkI.K(!UAIMI. 

The  two  methods  ol'  Mi-ranfrini;;  tiir  onliiciry  Mui-sc  ciiciiils  ;iiv  culled  tlie 
"  open  "  and  "  closed  "  cirouit  systems. 

The  latter  is  frequently  called  the  American  system,  a  diagn'am  of  which  is 
shown  in  figure  2-1.  In  this  oidy  one  line  battei-y  is  necessary,  although  in 
practice  it  is  found  better  to  divide  tlie  battery  l)etween  the  terminal  stations 
as  shown,  care  being  taken  hot  to  connect  the  batteries  in  opposition.  Each 
key  is  furnished  Willi  a  circuit-closer  lever,  and  when  tlie  line  is  not  in  use 
the  current  is  constantly  flt)wlng,  keeping  the  relays  and  sounders  closed. 
When  operator  at  any  station  opens  the  circuit  by  means  of  the  lever,  he  con- 


Fig.  2-1.— telegraph    SYSTEM.  CLOSED    CIRCUIT. 

trols  it  entirely  with  the  key.  This  system  is  In  univiTsal  use  in  the  United 
States  and  Canada. 

A  diagram  of  the  open-circuit  telegraph  system  is  shown  in  figure  2-2.  With 
this  system  each  station  must  have  sutiicient  main-line  battery  to  operate  all 
relays  in  the  circuit.  The  keys  have  a  front  and  back  contact  fsee  fig.  2-5). 
When  the  line  is  not  in  use  there  is  no  current  flowing  and  when  operating  key 
at  any  station  is  depre.ssed,  the  back  contact  of  that  key  is  opened' and  the 
main-line  battery  to  the  front  contact  is  placed  in  the  circuit  which  operates 
all  relays  on  the  line.  The  relay  is  sometimes  placed  in  the  line  connected  to 
back  contact,  in  which  case  the  home  relay  is  not  operated.  By  this  means  the 
resistance  of  the  circuit  is  diminished  approximately  li50  ohms,  which  is  the 
resistance  of  the  main-line  relay.  However,  the  American  operator  usually 
prefers  having  the  relay  connected  as  shown  in  the  diagram,  so  that  the  home 
relay  will  operate,  thereby  operating  the  home  sounder. 

This  system  has  been  used  exclusively  on  the  short  Signal  Corps  subma- 
rine cables.  It  obviates  the  constant  application  of  battery  to  the  cable, 
as  would  result  from  use  of  the  closed-circuit  system. 

(33)  1 


2  Signal  Corps  Manual  No.  3. — Chapter  2. 

Telegraph   Office  Equipments. 

Tlio  familiar  esstMitial  instruments  of  tl't'  ordinary  Morse  lolcj^raiili  ollicc 
need  hut  brief  mention,  as  it  is  assumed  that  tlie  reader  is  already  familiar 
witli  the  tirst  principles  of  telegraphy. 


Fig.  2-2.— TELEGRAPH     SYSTEM,    OPEN    CIRCUIT. 

The  ordinary  American  Morse  or  closed-circuit  key  is  shown  in  figure  2-3. 
The  lever  .1  is  ordinarily  of  steel  nickel  plated;  the  milled-head  screw  /•' 
adjusts  the  tension  of  the  sju-ing  below  it.     O  is  the  base  which  supports  the 


Fig.  2-3.— TELEGRAPH    KEY,    CLOSED   CIRCUIT,    LEG  TYPE. 

trumiioii    bearings   of   the   key.      .1/    is    the    circuit-closer    lever,    which    is    i)iv- 
oti'd    al    Ihe    rear    and    slips    undt  r    a    curved    melal    piece    »S',    which    is    insu- 


Flg.  2-4.— TELEGRAPH    KEY,   CLOSED   CIRCUIT     LEGLESS  TYPE. 


Telegraphy  and  the  Induction  Telegraph  Set. — Chapter  2. 


3 


late<l  from  tlie  base,  l)Ut  in  connoction  witli  the  front  leg  L.  This  front  leg 
is  (•oiiiicctcd  witii  tlie  ri-l:iy  and  tiie  \nirk  Ic^  //  to  tlie  battt-ry  or  olln-r  liiie 
if  it  is  a  "way"  ollitv.  ('  represents  tlie  uiipor  ami  lower  C'onta<-t  points  of 
piatiniuii,  this  iiictai  resistiiii,'  tlie  corroding;  action  of  the  spark  produced  on 
openin;^  the  l^t'y. 

The  lejiless  key  is  shown  in  fijjure  2-4.  The  binding  posts  instead  of  the  legs 
are  connected  to  line  and  battery,  respectively.  The  parts  corresponding  to  the 
leg  key  are  siuiilarly  lettered. 


Fig.  2-5.— TELEGRAPH    KEY,    OPEN    CIRCUIT,    LEG  TYPE. 

The  "open-circuit"  key  has  an  insulated  front  and  an' insulated  back  contact, 
and  the  circuit-closing  lever  is  dispensed  with.  As  shown  in  figure  2-5,  the 
screw  C  on  the  ba.se  of  the  key  is  connected  with  the  relay,  the  insulated  lower 
front  contact,  D,  with  the  battery,  and  tlie  insulated  back  contact,  E.  with  the 
ground  at  a  terminal  station  or  with  the  outgoing  wire  at  a  "way"  station. 

Tlie  o]K'n  circuit  key,  legle.ss  type,  may  also  be  supplied. 

THF,   1!KI..\V. 

The  function  of  the  relay  is,  briefly,  to  cause  a  comparatively  powerful  local 
current  tlirough  a  sounder  to  be  controlled  by  a  much  feeliler  one  in  the  main- 


Fig.  2-6.— TELEGRAPH,    RELAY,    r.". 


Lii 


line  circuit.  The  rehiy  coils  are  inchnU'd  in  the  main-line  circuit,  the  two  bind- 
ing posts  on  tlie  right  (fig.  2-0)  being  connected  with  the  key  anil  line,  respec- 
tively, the  bintling  posts  on  the  left  being  connected  with  the  s(»under  and  local 
battery,  respectively.     The  main  and  local  circuits  are  indicated  by  the  broken 

(35) 


4  Signal  Corps  Manual  No.  3. — Chapter  2. 

lines.     The  resistance  of  the  rekiy  coils  is  now  almost  universally  150  ohms, 
although  on  some  short  lines  a  "pony"  relay  of  20  ohms  is  used. 


Fig.   2-7.— TELEGRAPH,    BOX    RELAY. 

The  box  relay  with  the  key  on  the  base  is  shown  in  figure  2-7.  This  relay 
has  a  heavier  lever  for  giving  a  louder  sound  than  that  of  the  ordinary  relay, 
the  resonance  of  the  box  assisting.    As  it  may  be  used  at  temporary  field  offices. 


Fig.    2-8.— TELEGRAPH,    MAIN    LINE    SOUNDER. 

when  local  batteries  arc  not  (iltfaiiiablt>,  and  is  of  gri'at  sfrcMigtli  and  simplicity, 
it  is  a  most  useful  instrument  for  military  lines. 

The  "main-line  sounder"  (fig.  2-S)  is  somewhat  of  an  improvement  on  the 
box  relay.  The  coils  are  usually  wcuiid  lo  ITiO  (tlniis,  the  same  as  other  main- 
tine  in.strument.s. 

The  "pocket  relay"  is  a  c()mi)act  I'di-m  of  main-line  sounder  for  testing  pur- 
poses. About  40  milliamiicrcs  curri-nl  is  i'c(|iiirc(l  to  oju'rate  the  ir>0-<)lmi  instru- 
ment   to  best   advantage. 

THK    SOUNDER. 

This  well-known  instrument  is  shown  in  figure  2-9,  this  being  one  of  the 
most  common  foi-ms  now  in  use.  Its  connection  with  the  relay  and  local  battery 
circuit  has  already  been  indicated.  The  coils  are  usually  wound  to  a  resistance 
of  4  ohms,  and  it  requires  about  oiic-fourth  ampere  to  operate  the  sounder  as 
vigorously  as  is  recpilred  for  ordinar.v  ollices.  Hence  two  bluestone  cells,  each 
having  about  1  volt  10  M  F  and  2  olniis  internal  resistance,  will  give  the  required 
current. 


(^J-^;. 25-2^2+4/ 


(36) 


Telegraphy  and  tKe  Induction  Telegraph  Set.— Chapter  2.  5 

If  the  sounder  is  connected  in  circuit  with  colls  of  higher  E  M  F  an<l  lower  reeiat- 
aQce,  eome  resistance  wire  should  be  inserted  to  keep  the  current  down  to  one-fourth 


Fig.  2-9.— TELEGRAPH,  4-OHM    SOUNDER. 

ampere;  otherwise  the  battery  will  be  iised  up  wastefully.   For  example,  with  a  Fuller 

1  8 
cell  of  1.8  volts  E  M  Fand  one-fourt  hohm  internal  resistance,  7=j--j— =.42  ampere, 

which  is  considerably  more  current  than  necessary.     The  necessary  added  resist- 

1  8 
ance,  X,  can  be  found  as  follows:  Required  current  is  .25  ampere,  so  .25=    ."     „ 

4+i+A; 

1.06+. 25  X=1.8;  X='i  ohra.«.  the  '"dead  resistance"  to  be  introduced  in  circuit. 

In  cii.ses  when  a  nunilier  of  sounders  are  fed  from  one  storage  cell,  a  "  dead 

resistance"  of  4  olnns  .should  be  inserted  in  each  sounder  circuit,  as  the  storage 

ceil  lias  virtually  no  internal  resistance  and  an  E.  M.  F.  of  2  volts. 


SWlTCimOAUDS. 

These  are  either  terminal  or  intermediate  in  their  use,  and  as  there  is  con- 
siderable difference  in  extent  and  character  of  the  wiring  they  will  be  con- 
sidered .separately. 

The  intermediate  or  way-station  switchljoard  is  repi-esented  in  simplest 
form  in  figure  2-10.     Suppose  two  lines  coming  into  a  station  are  brought  to 


Fig.  2-10.— TELEGRAPH    SWITCHBOARD,    INTERMEDIATE. 
(37) 


:iGi567' 


6 


Signal  Corps  Manual  No.  3. — Chapter  2. 


tlie  tops  of  the  verticiil  strips  of  ln-iiss.  ;is  .shown,  usually  throui;h  lightning 
arresters.  Between  these  vertieal  strips  of  brass  are  vertical  rows  of  brass 
disks.  ;ill  the  disks  in  any  horizontal  row  being  connected  together  by  a  metal 
strip  on  tht'  back  of  the  board.  Semicircular  spaces  are  cut  atljoining  each 
other  in  the  strips  and  disks  so  connections  may  be  made  at  any  of  these 
points  between  the  disks  and  strips  by  the  insertion  of  conical  metal  plugs 
with  hard-rubber  heads.  By  means  of  these,  sets  of  instruments  may  be  con- 
nected up  with  each  other,  the  different  lines,  or  the  ground.  To  cut  out  a 
set  of  instruments  insert  plugs  at  21  or  22.  To  cut  in  the  upper  set  on  line 
No.  1  take  plug  out  of  21  and  insert  plugs  at  4  and  5  or  3  and  G.  To  cut 
upper  set  in  on  line  No.  2  remove  plugs  from  3,  4,  5,  6,  and  22  and  insert  them 
at  13  and  IG  or  at  14  and  15.  In  a  similar  manner  the  lower  set  of  office 
instruments  may  be  cut  in  on  either  line. 

Suppose  either  of  the  home  sets  is  cut  in  on  No.  1  line  and  an  open  circuit 
in  the  line  develops.  To  ascertain  whether  the  open  circuit  is  east  or  west 
of  the  station  proceed  as  follows :  Insert  plug  at  No.  2.  If  communication  is 
established  the  defective  line  will  be  east  of  station.  If  comnuinication  is  not 
established  insert  plug  at  No.  1,  when  communication  will  be  established  with 
.station  east  of  home  station  unless  both  lines  are  open.  The  foregoing  illus- 
trates the  use  of  the  ground  wire. 

Due  to  defects  in  one  of  the  lines,  the  main  office  may  desire  a  "  patch  " 
made.  This  means  that  it  is  desired  to  cross  connect  lines  1  and  2.  Suppose 
the  chief  operator  directs  that  line  No.  1  west  be  connected  with  line  No.  2 
east.  Of  course  it  is  desired  to  keep  one  of  the  sets  cut  in  at  this  oflice  on 
this  i)atched  line. 

Plugs  are  inserted  at  3  ami  IG  and  ail  otiier  1)1u.l;s  ai-e  removed. 

To  patch  No.  1  east  with  No.  2  west,  put  i)Iugs  at  4  and  15. 

To  loop  No.  1  west  with  No.  2  west,  put  plugs  at  3  and  15,  if  desired  to 
leave  instrumenis  in.  II'  desired  in  k'ave  them  out,  insert  ]ilug  at  ll>  instead 
of  at  15. 

If  directed  to  ground  tliis  looj),  as  may  be  needed  sometimes  in  testing,  insert 
a  plug  at  either  1  or  11. 

The  simi)lest  foi'ni  of  ofliee  switch,  called  a  i)lug  cut-out,  i.s*  shown  in  figure 
2-11.     The  lini>  wires  come  in   from  above,  the  wires  to  instruments  come  out 


Fig.  2-11.— TELEGRAPH,    PLUG    SWITCH    AND    LIGHTNING    ARRESTER. 

iielow.  and  llie  cenlral  wire  leads  to  ground.  Tli«>  insertion  of  the  plug  in 
the  lower  holes  groinids  "  cast  "  oi-  "wesi,"  .-md  when  in  the  >ij)iter  hole  cuts 
out  the  .statittn.  The  central  ;;round  jiliile  near  the  line  strips  acts  as  a 
lij;htninu  arrester. 

(88) 


Telegraphy  and  the  Induction  Telegraph  Set. — Chapter  2.  7 

LIGHTNING    ARRESTERS. 

The  principle  in  seneral  nj)on  wliich  tliesf  aiv  nuule  is  to  itrinj:  tlio  line 
or  some  of  tlie  first  metal  parts  to  wliich  it  is  coiinocted  in  tlie  odice  rlose 
to  a  conductor  connected  directly  to  the  ground.  Tlie  lij,'htninn  jumps  to  this 
ground  coiuiection  instead  of  going  througli  the  instruments.  Tliese  arresters 
are  frecpiently  parts  of  the  switchboard,  consisting  of  a  metal  plate  connected 
to  the  ground,  extending  across  the  vertical  line  strtips  and  not  quite  touching 
tliem,  or  of  a  series  of  I)rass  disks  extending  closely  over  tlie  stra)ts.  the  dislvs 
l)eing  all  connected  fo  tli(>  gi-ound  wire.  A  simple  form  of  arrester  is  shown 
in  tigiu-e  li-ll,  lieing  part  of  the  plug  cut-out. 

Tlie  Mason  llglitning  arrester,  fully  described  in  chapter  C,  of  ibis  niamial, 
is  sometimes  used  in  protecting  telegraph  apparatus,  and  cables  where  connec- 
tion is  made  to  aerial  llne.s. 

Terminal  Ofiick  Switchhoaiu)  and  IIattkuy  Ai;kan(;kments. 

The  general  jilan  of  the  terminal  swltcliboard  is  shown  in  ngure  li-12.  intro- 
ducing a  row  of  spring  jacks  at  the  bottom  of  the  board.  Tlie  method  of  utili/-- 
ing  these  in  cutting  in  sets  of  instruments  by  insertion  of  the  double  flat  plugs 
is  shown.  These  flat  plugs,  with  hard-ruliber  insulation  between  the  metal 
strips  composing  them,  are  connected  with  flexible  insulated  double-conducting 
cords  leading  to  the  sets  of  instruments.  It  will  be  seen  that  each  line  comes 
in  through  a  fuse  wire  to  the  top  spring  contact  of  the  jack,  and,  if  no  plug  is 
inserted,  passes  through  the  back  contact  and  up  to  one  of  the  vertical  straps 
of  the  board.  The  insertion  of  a  round  conical  plug  at  the  appropriate  disk 
connects  it  to  the  battery  and  ground.  The  insertion  of  a  flat  plug  and  cord 
leading  to  a  set  will  introduce  that  instrument  into  the  circuit.  The  various 
arrangements  for  interconnecting,  the  provision  for  duplex  and  repeater  sets, 


13     K-     15     IS 


2DISCI9 


Fig.  2-12.— TELEGRAPH    SWITCHBOARD,   TERMINAL  TYPE. 
(39) 


8 


Signal  Corps  Manual  No.  3. — Chapter  2. 


and  the  connections  for  loop  switches  can  be  studied  out,  especially  if  the 
reader  will  consult  Maver's  American  Telegraphy  and  Jones's  Pocket  Edition 
of  Diagrams,  etc.,  both  of  which  have  been  consulted  in  preparing  the  diagrams 
and  above  descriptions. 

As  most  modern  terminal  and  repeating  offices  are  now  provided  witli  storage 
battery  and  dynamo  sources  of  current,  the  method  of  supplying  the  terminal 
switchboard  and  its  connecting  lines  will  be  described  in  the  general  scheme 
outlined  in  figure  2-13. 

With  the  wire  E  F  disconnected  and  the  +  and  —  mains  connected  as  shown 
in  the  dotted  lines,  the  cells  are  connected  to  the  dynamo  in  two  rows  in  parallel 
for  charging.  When  completely  charged  they  are  disconnected  at  C  and  D  and 
reconnected  by  E  F.  This  puts  the  GO  cells  in  series  again  with  the  negative 
end  to  ground.  At  various  points  (10,  20,  30,  etc.)  taps  are  taken  off,  through 
incandescent  lamps  introduced  as  safety  resistances,  to  various  horizontal  rows 
of  disks  on  the  switchboard.  Tims,  beginning  at  the  top,  this  row  of  disks  is 
at  the  highest  potential  (120),  and  a  conical  plug  inserted,  connecting  any  disk 
of  this  row  with  the  line  leading  to  the  vertical  strap  through  the  jack  at  the 
bottom,  will  give  the  strongest  current,  and  so  on  down  the  rows  to  10.  which 
brings  into  the  circuit  only  the  last  5  cells  next  to  the  grounded  end  of  the 
battery.  The  low  internal  resistance  of  the  storage  battery  permits  feeding 
almost  any  number  of  lines  out  of  the  same  row  of  cells  without  interference. 
The  introduction  of  lamp  resistances  is  necessary  because  of  this  low  internal 
resistance  of  the  cells,  as  a  grounding  of  the  line  close  to  the  terminal  office 
would  otherwise  cause  a  current  dangerous  to  the  instruments.  The  amount 
of  lamp  resistance  to  be  inserted  at  each  potential  is,  according  to  Jones,  in  his 


Switchboai^d 

jo; 

p 
p 
p 
p 
p 
p 
p 
p 
p 
b 


Ij 

+1     120  Volts 

■— W 

I      110 


I 


100 


60 


.  1^  /--^iHiiii 'iN'l'l'NTl'l'l'l'l'l'N1'l'l'l'l'l'l"l'|fF 
iS^   + — D 


50 -\- 


II 1 1 1 1 11 1 


40 


I  I  11     I  I  I  I 


30 


20 


I  III 


/O 


li  1 1  |^=Y 


Fig.  2-13.— TELEGRAPH    SWITCHBOARD,    POWER   CONNECTIONS. 

Pocket  Edition  of  Dingrnnis.  etc.,  2  ohms  for  each  volt.  One  ordinary  16- 
candlepower  liimp  would  he  iiliout  right  for  (he  110-volt  poteiithd,  and  two  of 
thc.'ic  in  parallel  for  the  TiO-volt  potential. 


(40) 


Telegraphy  and  the  Induction  Telegraph  Set. — Chapter  2. 
Telegkai'h  Repeaters.' 


THE    MILLIICEN    REPEATEU. 


This  was  one  of  the  earliest  repeaters  introihir-ed  into  the  telegraph  .service, 
and  it  is  still  a  standard  repeater  of  the  i)rinclpal  telepraph  conii)jinies  of 
this  country.  The  Siirnal  Corps  has  a  nunilter  in  use  in  connection  with 
telegraph  lines  in  Alaska. 


This  repeater  may  iiiMliaps  he  termed  an  automatic  electromechanical  re- 
peater, lor,  while  electricity  is  the  control liiii,'  force  in  the  performance  of 
its  automatic  functions,  the  ultimate  action  is  mechanical. 

Figure  2-14  is  a  theoretical  diagram  of  the  connections  of  the  Milliken  re- 
peater.    R  and  R'  are  the  main-line  relays.     EM  and  FAI'  are  extra  magnets, 

1  The  descriptions  and  diagrams  of  the  Milliken  and  Weiny  repeaters  are  taken  by  per- 
mission from  Maver's  American  Telegraphy. 


(41) 


10  Signal  Corps  Manual  No.  3. — Chapter  2. 

■which  in  practice  are  supported  on  metal  standards  that  liold  them  rigidly 
in  their  respective  positions  relative  to  the  main-line  i-elays.  The  armature 
levers  of  the  extra  relays  are  pivoted  at  the  top  as  shown.  T  and  3"  are 
transmitters.  The  levers  L  h'  of  the  transmitters  are  insidated  from  the 
tongues  X  x'  at  points  i  i'  and  from  screw  posts  F  F'  hy  small  pieces  of  hard 
rubber. 

The  working  of  this  repeater  may  perhaps  be  best  described  by  assmning  that 
the  east  is  about  to  send.  To  that  end  he  opens  his  key  ;  that  opens  relay  R'  and 
its  lever  V  falls  back,  as  in  the  figure,  and  opens  the  local  circuit  controlling 
the  transmitter  7".  As  the  latter  instrument  opens,  it  breaks  the  local  circuit 
of  FM  at  a' ;  the  retractile  spring  8  of  extra  magnet  EM  at  once  pulls  its  lever 
against  the  lever  I  of  relay  R  as  in  figure,  and  the  transmitter  T'  opens  the 
western  circuit  at  x' ;  this  demagnetizes  relay  R,  and  its  spring  would  withdraw 
its  lever  I  from  its  front  stop  /,  thereby  opening  the  transmitter  T,  and  conse- 
quently the  eastern  circuit  at  x,  but  that,  as  already  stated,  the  lever  of  EM  is 
against  lever  I,  holding  it  on  its  front  stop,  and  thus  keeping  the  local  circuit 
of  T  closed.  AYhen  the  east  again  closes  his  key,  relay  R'  also  closes;  conse- 
quently so  does  T' .  This  action  closes  EM,  and  the  lever  of  that  intrument  is 
withdrawn  from  its  position  against  the  lever  R.  This  releases  R's  lever,  but, 
as  now  the  western  circuit  is  closed  at  x' ,  the  lever  /  is  held  forward  by  its 
armature. 

In  this  way  the  function  of  the  repeater  in  keeping  closed  the  opposite  trans- 
mitter, and  virtually  also  the  circuit  which  is  being  "repeated"  into,  is  per- 
formed. 

Should  the  west  now  desire  to  "  break  "  or  send  to  the  east,  he  opens  his  key, 
which  action,  by  opening  the  local  circuit  of  transmitter  T  at  F,  opens  the 
eastern  circuit  at  x.  The  east,  finding  his  circuit  now  open,  closes  his  key  to 
await  the  remarks  of  the  west,  when  the  "repeating"  actions  just  described  are 
reversed. 

THE    MEINY    EKl'EATER. 

Tliis  repeater,  which  is  in  operation  on  the  lines  of  the  United  Press,  the 
Postal  Telegraph  Co.,  and  Signal  Corps,  is  shown  in  figure  2-1.1.  The  opposite 
transmitter  is  kept  closed  at  the  repeating  station  by  the  action  of  an 
extra  magnet  added  to  the  main-line  relays,  the  construction  and  operation 
of  wlucii  is,  briefly,  as  follows:  Tlie  extra  magnet  is  wound,  as  shown,  Avith  two 
coils,  through  which  a  current  fiows  from  a  local  battery  in  opposite  directions 
around  the  core,  so  that  the  latter  is  normally  not  magnetized.  When,  how- 
ever, one  of  these  extra  coils  is  opened  the  current  in  the  other  coil  magnetizes 
the  core.  The  wire  which  is  joined  to  both  coils  of  the  extra  magnet  goes 
directly  to  tlie  ri^ht-hand  end  of  the  opposite  local  battery.  The  other  end  of 
each  coil  passes  to  the  other  jmlc  of  the  same  battery,  (uic  coil  by  way  of  the 
left  side  of  frame  and  the  other  by  way  of  the  lever  of  the  opposite  -trans- 
mitter, as  sJiown.  This  lever  is  insulated  from  the  left-hand  post  when  the 
transmitter  is  open,  (^onsetpiently,  when  the  left-hand  transmitter  is  open,  as 
in  figure,  the  circuit  of  the  left-hand  coil  of  the  extra  magnet  of  the  eastern 
relay  is  open  at  the  left-liand  post  of  the  western  transmitter,  and  as  a  result 
thereof  that  extra  magnet  is  magnetized  by  the  current  passing  through  the 
right-band  coil,  and  licence  the  armatuic  lever  of  th.il  n^lay  is  held  against  its 
front  sloj).  Thus,  for  exairiple,  when,  as  in  the  figure,  the  west  sends  to  the 
east,  and  thereby  opens  his  key,  the  western  relay  in  the  repeating  office  opens 
and  its  armature  lever  falls  back,  o])eniMg  the  local  circuit  of  the  western  trans- 

(42) 


Telegraphy  and  the  Induction  Telegraph  Set. — Chapter  2. 


11 


niitter.  As  this  transmitter  opens  it  first  breaks,  at  its  left-hand  post,  the  cir- 
cuit of  the  left-hand  coil  of  tlie  extra  magnet  of  the  eastern  relay,  and  next 
opens  the  eastern  main-line  circuit  at  the  right-hand  post.  As,  however,  the 
armature  of  the  eastern  relay  is  ivcpt  closed  in  the  manner  stated  by  its  extra 
magnet,  the  eastern  circuit  remains  unbroken  in  the  repeating  station. 


i  I ^_^_  i , 


The  local  battery,  it  will  be  seen,  is  also  utilized  to  operate  its  respective 
transmitter.  A  button  switch  is  phiced  on  the  base  of  each  transmiter  for  the 
purpose  of  short-circuiting  the  main-line  contact  points  on  the  transmitter 
when  it  is  desired  to  use  the  transmitter  simply  as  a  sounder  for  the  relay. 

Figures  2-16  show  the  circuits  of  a  telegraph  repeater  which  is  usetl  in  rej^at- 
ing  signals  from  open-circuit  telegraph  systems  to  closed-circuit  telegraph 
systems,  or  vice  versa. 


46581°— 17 


(43) 


12 


Signal  Corps  Manual  No.  3. — Chapter  2. 


Operation. — The  illustration  shows  the  normal  position  of  all  instruments 
when  receiving. 

To  send  from  open-circuit  station,  move  tlie  two-point  switch  to  battery ;  this 
puts  current  to  line  through  back  contact  of  key.  Close  the  key ;  this  takes 
battery  from  line,  thus  permitting  the  spring  to  withdraw  the  armature  from 


0=0^^ 


T  C/osed  Circuit 

i:  StaUon 


Fig.   2-16.— TELEGRAPH    REPEATER    CIRCUITS    FOR    O.    C.    AND    C.    C.    OPERATION. 


relay  No.  2,  closing  the  local  .rounder  circuit  at  its  baclv  contact.  At  the  same 
tin)e  relay  No.  4  is  deenergized,  permitting  its  armature  to  close  the  circuit  for 
the  closed-circuit  station  at  its  back  contact.  Thus  it  is  seen  that  closing  the 
open-circuit  key  causes  its  sounder  to  close,  at  the  same  time  closing  the  distant 
closed  station.  Now  open  the  open-circuit  key.  This  puts  the  battery  to  line, 
which  causes  the  armature  of  relay  No.  2  to  be  attracted,  which  opens  the  local 
circuit  of  its  sounder ;  at  the  same  time  the  armature  of  relay  No.  4  is  attracted, 
which  opens  the  circuit  for  the  open-circuit  station.  Thus  it  is  seen  that  a  signal 
at  the  open-circuit  station  is  reproduced  at  the  closed-circuit  station.  When 
through  sending,  move  two-point  switch  to  the  other  stop  —  to  ground. 

To  send  from  the  closed-circuit  station,  open  the  key,  which  opens  the  local 
sounder  circuit ;  at  the  same  time  relay  No.  H  is  demagnetized,  thus  permitting 
its  relay  to  clo.se  a  local  circuit  at  its  back  contact.  A  local  battery  energizes 
relay  No.  3,  which  attracts  its  armature,  thus  closing  a  circuit  for  a  battery 
to  energize  the  open-circuit  station,  relay  No.  2;  this  opens  the  sounder  circuit 
at  that  station. 

Now  close  the  key.  This  closes  the  local  sounder  circuit;  relay  No.  5  attracts 
its  armature,  thus  opening  the  local  circuit  for  relay  No.  3.  The  latter  is  thus 
deenergized  and  permits  the  retractile  spring  to  withdraw  the  armature  from 
Its  front  contact,  tbus  eliminating  all  battery  from  tlie  open-circuit  line;  then 
relay  No.  2  permits  its  iiniiiilui-c  1<i  cIdsc  the  DiKMi-circnit  sounder  circuit  at 
its  back  contact. 

It  is  now  seen  that  signals  sent  fnmi  fillicr  sliilion  arc  aulimiatically  repeated 
to  the  other. 

(44) 


Telegraphy  and  the  Induction  Telegraph  Set. — Chapter  2.  13 

The  two  lines  are  always  in  an  oppoate  electrical  state,  which  tiioy  shoulil  be. 

The  closed-circuit  station  has  the  ordinary  apparatus. 

The  open-circuit  station  must  reverse  the  contacts  of  its  relay  ami  connect 
battery  to  line  on  its  !)ack  contact;  also,  it  requires  a  two-way  switch  to  <ut  out 
battery  when  not  sending;. 

If  desired,  a  combination  key  may  be  utilized  for  the  ordinary  oi»en-circuit  key  ; 
in  this  case  he  two-point  switch  shown,  is  not  required. 

For  best  results  relay  No.  5  shoiUd  be  the  same  kind  as  No.  6.  Also  rehiy 
No.  4  should  be  the  same  kind  as  No.  2.  No.  3  may  be  of  any  desired  resistance 
or  nature,  as  it  is  on  an  independent  local  circuit. 

No.  5  relay  is  in  the  closed-circuit  line,  and  No.  4  relay  is  in  the  open-circuit 
line. 

The  local  sounder  battery  at  the  open-circuit  station  nmst  be  a  closed-cinuii 
one.     The  other  butteries  are  all  of  the  open-circuit  type. 

The  followin.i;  should  i)t'  observed  in  tiie  adjustment  and  care  of  telegraph 
repeaters: 

The  distance  between  cores  of  magnets  and  armature  operated  thereby  sliould 
be  no  si'pater  than  necessary  to  i>revent  armature  from  stiekins.  Controlling 
mafinets  once  adjusted  for  obtaining  maximum  strength  seldom  require  further 
adjustment. 

Adjustments  should  be  so  line  that  a  considerable  change  in  the  temi>era- 
ture  of  the  room  will  so  alter  the  distance  between  contact  points  that  they 
will  require  readjustment.  With  such  adjustments  a  particle  of  dust  will  some- 
times bridge  the  contact  points,  and  they  should  be  cleaned  daily,  or  more 
frequently  if  necessary. 

An  extra  relay  in  each  circuit  at  repeater  stations  makes  it  possible  for  a 
repeater  attendant  to  know  beyond  doubt  just  how  the  signals  are  received  at 
distant  stations.  This  obviates  depending  on  the  varying  judgment  of  men  at 
different  stations.  He  can  send  rapid  signals  and  observe  exactly  how  they 
pass  through  repeaters. 

The  repeater  should  be  so  located  that  contacts  are  readily  accessible  and 
that  light  can  be  seen  between  the  contact  points  or  reflected  to  them  by  means 
of  white  paper,  thereby  obtaining  the  same  result.  The  repeating  point  of  the 
repeating  sounder  armature  is  on  a  spring  which  admits,  if  the  adjustment  is 
correct,  the  repeating  point  to  be  opened  only  after  the  rigid  points  on  this 
armature  which  control  the  extra  or  controlling  magnets  have  opened. 

TEST  FOR  OPERATION  OF  TELEGRAPH  REPEATERS. 

A  thorough  knowledge  of  the  operation  of  telegraph  repeaters,  personal  inter- 
est, and  a  comparatively  small  amount  of  time  are  necessary  in  order  that 
attendants  may  becoiue  proficient  in  the  care  of  telegraph  repeaters. 

MILLIKEN    REPEATERS. 

Figure  references  below  refer  to  figure  2-14.  The  extra  relay  in  each  circuit 
at  repeater  station  reconuuended  in  the  foregoing  is  not  shown  in  tigure  2-14. 

Slowly  raise  the  left  end  of  the  armature  of  the  repeating  sounder  T'.  This 
will  break  the  circuit  of  the  controlling  magnet  EM.  and  the  return  of  its 
armature  will  be  distinctly  heard.  The  next  instant  the  spring  contact  x'  of  the 
repeating  sounder  T'  will  be  opened,  thereby  opening  the  circuit  leading  to 
the  relay  A*,  extra  relay  (not  shown),  and  line.  The  oi)eniug  click  of  the  arma- 
ture of  the  extra  relay  will  be  distinctly  heard.  It  will  be  notinl  that  in  the 
above  operation  the  armature  of  the  relay  If  is  held  in  the  closed  ixisition  by 
the  armature  of  the  extra  magnet  EM  even  though  tlSe  relay  R  be  deeuergized. 

(45) 


14 


Signal  Corps  Manual  No.  3. — Chapter  2. 


REVERSE  OPERATION. 

Upon  lowering  by  hand  the  armature  of  the  repeating  sounder  T',  the  spring 
contact  will  first  be  closed  and  at  the  same  instant  the  closing  of  the  arma- 
ture of  extra  relay  mentioned  above  will  be  heard.  At  the  next  instant  the 
rigid  contact  points  A'  close,  thereby  closing  the  circuit  to  the  extra  magnet 
E  M.  This  draws  the  extra  magnet  armature  away  from  the  armature  L  of 
relay  R. 

WEIXV    REPEATERS. 

With  Weiny  repeaters  the  effect  is  the  same ;  the  opposite  controlling  arma- 
ture, instead  of  falling  back  as  in  the  Rlilliken,  is  held  in  position  due  to  the 
opening  of  one  winding  only  of  the  two  differentially  wound  coils  of  the  magnet. 
This  fact  is  indicated  by  a  sound  emanating  only  from  its  armature.  In  rapid 
sending  the  difference  between  the  opening  and  closing  of  rigid  and  springy 
contact  points  can  not  be  detected,  but  nevertheless  the  difference  must  exist 
l)efore  the  repeaters  will  operate  satisfactorily,  for  should  both  open  simul- 
taneously, uneven,  ragged  signals  will  result. 

Duplex  Telegraphy. 

[t'ondenst'd  from  "American  Telegraph  I'ractice,"  McNicol.] 

By  duplex  telegraphy  is  meant  a  system  which  makes  possible  the  transmis- 
sion of  two  messages  over  a  single  wire  at  the  same  time,  one  in  each  direction. 

THE    SINGLE-CURRENT    UUPLEX. 

The  most  important  elements  of  the  single-current  duplex  are  the  trans- 
mitter, the  differential  relay,  the  artificial-line  rheostat,  and  the  condenser. 


LINE 


Fig.  2-17.— TELEGRAPHY,   DUPLEX,   SINGLE  CURRENT,   THEORETICAL  CONNECTIONS. 

The  single-current  duplex  is  sometimes  referred  to  as  the  Stearns  duplex,  in 
lioiior  of  the  inventor,  Mr.  Joseph  B.  Stearns. 

Ill  single  Morse  circuits,  the  armatures  of  all  relays  in  the  circuit,  including 
tliat  at  the  home  station  and  that  at  the  distant  station,  are  operated  simul- 
taneously when  any  signaling  key  connected  into  the  circuit  is  manipulated. 

When  it  is  required  to  tran.smit  a  message  in  each  direction  over  a  line 
simultiineously,  it  is  evident  that  the  receiving  relay  at  each  of  the  two 
terminal  stations  nuist  resjxtnd  to  the  maniitulations  of  the  signaling  key  at 
the  distant  station,  and  not  to  the  oiteration  of  the  key  at  the  home  stalion. 

Figure  2-17  is  a  diagram  of  the  llieoretical  connections  of  the  single-current 
duplex.  \  line  is  shown  extending  l»etween  stations  A  and  li.  T  and  T'  are 
the  transniitters,  l>li  and  DIV  the  different  i.il  relays,  ,4/^  and  Alt'  the  artiflcial- 

(46) 


Telegraphy  and  the  Induction  Telegraph  Set. — Chapter  2. 


1") 


line  i^ieostats,  and  b  and  h'  tlie  main-line  batteries  at  A  and  /{  resiieciively. 
The  nmction  of  the  transmitter  is  simply  that  of  a  sifjnalinK  key  (•nnneeteil 
into  the  mainline  cireuit  in  such  a  manner  that  when  the  key  is  eloscd  haltery 
is  applied  to  the  line,  and  when  the  key  is  (ji»ened  the  liiu'  is  jirounded. 

Fij:ure  2-18  shows  a  k«'y  eonnectwl  into  the  niain-liu(>  circuit  direct,  to  do 
the  work  of  a  transmitter.  Here,  as  in  the  case  of  the  transmitter  shown 
in  figure  2-17,  it  is  apparent  that  wlien  the  key  is  depressed,  battery  is  ap- 
plied to  the  line,  and  when  the  key  is  openetl  the  line  is  grounded. 

In  the  operation  of  duplexes — as  will  be  explained  more  fully  later — it  i.« 
essential  that  in  the  operation  of  the  transmitter  or  of  the  key  the  shortest 
possible  interval  of  time  shall  elapse  between  the  instant  battery  is  removed 
from  the  main  line  and  the  instant  the  ground  connection  is  substituted  there- 
for. Obviously  if  an  ordinary  key  were  used  to  control  the  application  of 
battery  and  removal  of  ground  connection,  and  vice  versa,  in  the  act  of  signal- 
ing, the  lapse  of  time  between  these  two  contacts  would  be  excessive,  due  to 
the  comparatively  slow  movement  of  the  hand  in  working  the  key,  being  more 
pronounced  the  wider  the  gap  maintained  between  the  contacts  of  the  key. 
Also,  were  the  ordinary  key  useil  directly  in  the  line  circuit,  the  speed  of 
operation  would  be  considerably  curtailed  owing  to  the  requirement   imposed 


Fig.    2-18.— TELEGRAPHY,     DUPLEX,     SINGLE 
CURRENT,  THEORETICAL  CONNECTIONS. 

upon  the  operator  to  make  equally  firm  and  solid  contact  between  the  key 
lever  and  the  ground  connection  as  between  the  lever  and  the  battery  contact ; 
a  condition  that  the  average  operator  would  find  quite  difficult  to  meet. 

The  transmitter,  therefore,  is  used  for  the  purpose  of  insuring  instantane<nis 
transfer  of  the  line  connection  from  battery  contact  to  ground  contact  in 
response  to  the  operation  of  the  key  which  controls  the  operation  hu-ally  of  the 
transmitter,  regardless  of  whether  the  key  is  operati'd  rapidly  or  slowly. 

By  noting  the  construction  of  the  transmitter  shown  in  connection  with  the 
diagram,  figure  2-17.  it  may  be  .seen  that  the  moving  element  of  the  instru- 
ment may  be  so  adjusted  that  at  the  instant  the  battery  is  removetl  the  ground 
contact  is  made,  and  thus  the  continuity  of  the  line  is  pre.serve«l,  or.  in  other 
words,  the  period  during  which  the  line  is  open  is  reduced  to  a  minimum.  This 
is  a  requirement  of  considerable  consequence  in  the  operation  of  nniltiplex 
telegraphs. 

All  that  is  required  in  a  differential  relay  is  that  when  currents  of  c«iual 
strength  pass  through  both  windings  of  the  differential  magnet,  the  cores  shall 
not  become  magnetized.  It  is  to  be  remembered,  however,  that  the  amount 
of  magnetism  produced  in  either  core  is  directly  dependent  upon  the  strength 
of  current  flowing  in  the  winding  around  the  core,  and  if  the  magnetic  effect 


(47) 


16 


Signal  Corps  Manual  No.  3. — Chapter  2. 


produced  by  one  of  the  coils  is  to  be  exactly  neutralized  by  that  of  the'*other, 
it  is  essential  that  the  current  strength  in  the  two  coils  be  equal. 

If  the  current  strength  in  one  coil  is  greater  than  that  in  the  other  coil, 
naturally  the  excess  current  produces  a  certain  anH)unt  of  magnetism  which 
is  not  neutralized  and,  due  to  this  magnetism,  the  armature  of  the  relay  is 
attracted. 

It  is  already  understood  that  the  strength  of  the  current  flowing  in  a  cir- 
cuit is  dependent  upon  the  value  of  the  applied  e.  m.  f.  and  upon  the  ohmic 
resistance  of  the  circuit.  In  the  case  of  the  differential  relay,  therefore,  it  is 
essential  that  if  the  relay  is  to  be  truly  differential  the  current  strength  in 
both  windings  must  be  identical,  and  this  in  turn  imposes  the  requirement  that 
the  resistance  of  each  circuit  must  be  identical. 


Fig.    2-19.— TELEGRAPHY,     DUPLEX,    SINGLE 
CURRENT,  THEORETICAL  CONNECTIONS. 

Suppose  a  differential  relay  having  a  resistance  of  200  ohms  in  each  winding 
is  connected  with  a  source  of  e.  m.  f.  so  that  current  flows  through  both  coils 
as  indicated  in  figure  2-19.  If  it  is  required  that  the  cores  of  the  relay 
magnets  shall  not  be  magnetized,  it  is  necessary  that  equal  current  values 
obtain  in  each  of  the  divided  paths  to  ground.  The  fact  that  the  resistance 
of  each  of  the  relay  coils  "is  the  same  is  of  little  consequence  unless  the  circuits 
beyond  the  relay  also  are  of  equal  resistance. 

In  figure  2-19  current  passes  through  one  coil  of  the  relay  and  beyond 
through  a  line  wire  having  1,000  (»hms  resistance,  thence  to  ground.  The  other 
coil  of  the  relay  forms  a  portion  of  a  path  to  ground  through  a  resistance  coil 
of  800  ohms.  It  is  evident,  therefore,  that  as  the  current  divides  at  S,  it  has 
two  paths  to  ground,  one  having  a  resistance  of  1,000  ohms  and  the  other  a 
resistance  of  1,200  ohms,  and  it  is  apparent  that  tliere  will  be  more  current 
flowing  in  the  circuit  having  less  resistance  than  in  the  oilier.  As  a  con.se- 
quence,  one  core  of  the  relay  is  to  a  certain  extent  magnetized,  due  to  the  (>xtra 
cuii-fiil   in  one  C(»il  of  tiie  relay  over  that  in  the  other  cdil. 

The  resistance  of  main-line  wires  varii'S  from  a  lew  Iniiidi-cd  oliiiis  to 
several  tliousand  olims  iiml  wliere  dilVerentiMl  relays  ai-c  used  in  duplex 
operation,  in  ordri-  to  iiisurt'  tiiat  equal  (MU'reiit  \nlues  ohlaiii  in  eni'h  coil  of 
the  rehiy  wlien  llie  lioine  liallei-y  is  ai>plie(l  lo  llie  line  .•irnl  llie  distant  (Mid  of 
the  line  is  grounded,  it  is  neeessai\v  to  liave  at  tlie  lioiiie  station  an  ad.justal)le 
resistance  Ihi'ougli  wiiiili  the  other  coil  of  (he  relay  may  be  connected  to 
ground. 

Obviously  if  this  resistance  is  adjusted  to  have  a  \aliie  e(iiial  to  lliat  of  the 
line  wire  to  the  distant  station,  like  current  values  will  exist  in  both  coils  of 
the  relay,  and  there  will  not  be  any  magneti.sm  produced  in  the  cores  of  the 
relay. 


(48) 


Telegraphy  and  the  Induction  Telegraph  Set. — Chapter  2.  17 

The  adjustable  resistance  used  le  e([uate  the  resistance  of  llie  niain-line  wire 
is  generally  called  the  artificial  liiu'. 

TllK    AKTIKICIAI.    l.INK. 

All  line  wires  possess  electrostatic  capacity.  The  quantity  of  electric  charge 
accumulated  upon  the  surface  of  the  conductor  depends  upon  the  superficial 
area  of  the  conductor,  upon  the  distance  intervening  between  the  conductor 
and  the  earth  (or  between  the  conductor  concerned  and  other  conductors  in 
electrical  contact  with  the  earth),  and  upon  the  nature  of  the  insulating 
medium  intervening  between  the  line  wire  and  the  earth.  In  any  line  of  con- 
siderable lenf^th  a  portion  of  the  current  is  l)ound  up  in  the  form  of  static 
charge. 

The  first  rush  of  current  into  the  line  at  the  instant  the  battery  is  applied 
thereto  (sometimes  referred  to  as  the  current  of  charge)  for  an  instant 
produces  a  much  greater  magnetic  effect  upon  the  armature  of  the  h(jme  relay 
than  obtains  wlieu  the  entire  line  has  been  fully  charged  and  permanent  con- 
ditions established  in  the  circuit. 

The  result  of  the  initial  inrush  of  current,  greatly  exceeding  in  volume,  as 
it  does,  the  final  current,  is  that  a  false  signal  or  "  kick  "  of  the  relay  armature 
is  produced.  The  energy  of  the  kick  depends  upon  the  electrostatic  capacity 
of  the  line,  being  gi-eater  where  the  capacity  is  high,  and  less  pronounced  as 
the  static  charge  taken  on  by  the  line  wire  is  less. 

Also,  there  is  to  be  considered  the  effect  of  static  discharge,  which  occurs 
at  the  instant  the  line  wire  is  shifted  from  the  battery  connection  to  the 
ground  connection  upon  opening  the  key  controlling  the  operation  of  the 
transmitter.  At  this  instant  the  electrostatic  charge,  which  has  been  accumu- 
lated upon  the  surface  of  the  conductor,  flows  back  to  ground  by  way  of 
the  ground  contact  of  the  transmitter,  passing  tlu-ough  the  main-line  coil  of 
the  differential  relay,  again  producing  kick  of  the  relay  armature. 

In  view  of  these  considerations,  therefore,  it  is  necessary  if  the  false  sig- 
nals which  are  produced  at  the  beginning  and  the  end  of  each  intended  signal 
are  to  be  neutralized  or  nullified  that  the  artificial  line  be  made  to  possess 
properties  identical  with  those  of  the  main-line  wire;  i.  e.,  resistance  and 
capacity. 

The  application  of  the  condenser  as  an  adjunct  of  the  artificial  line  gives  to 
the  latter  the  desired  property  of  electrostatic  capacity. 

A  condsenser  path  to  ground  via  the  artificial-line  coil  of  the  differential 
relay  results  in  an  initial  rush  of  current  through  that  coil  at  the  instant  bat- 
tery is  applied  to  the  line,  which,  by  means  of  adjustalile  "  timing  "  resistances 
in  series  therewith,  may  be  made  to  exactly  equal  in  strength  and  duration  the 
corresponding  rush  of  current  which  takes  place  at  the  same  instant  through 
the  main-line  coil  of  the  relay,  thus  at  the  critical  moment  insuring  identical 
current  values  in  both  coils  of  the  relay. 

And,  further,  when  the  line  wire  is  shifted  from  battery  contact  to  the 
ground  connection,  at  the  moment  the  key  is  opened  the  discharge  from  the 
condenser  associated  with  the  artificial  line  takes  place  through  the  relay 
coil,  forming  a  portion  of  the  artificial-line  circuit  at  the  same  instant  that  the 
main  line  discharges  through  the  relay  coil,  forming  a  portion  of  the  main-line 
circuit,  thus  again  at  the  critical  moment  insuring  equal  current  values  in  the 
two  coils. 


(49) 


18  Signal  Corps  Manual  No.  3. — Chapter  2. 

To  understand  the  import  of  the  above  remarks,  one  must  have  in  mind 
the  positions  of  the  main-line  circuit  and  of  the  artificial-line  circuit  throuj^li 
tlie  windinjrs  of  the  respective  rehiy  coils,  also  that  the  magnet  made  up  hy 
the  artiticial-line  relay  coil  and  the  magnet  made  up  liy  the  main-line  relay 
coil  both  control  the  same  armature. 

When  the  relay  is  operated  by  current  from  the  distant  station  its  operation- 
is  due  to  a  surplus  of  current  in  the  main-line  coil  over  wliat  may  be  in  the 
artificial-line  coil  of  the  relay. 

When  the  signaling  keys  at  each  end  of  the  line  are  closed  and  like  poles 
of  battery  are  applied  at  both  ends  of  the  line,  the  desired  signal  is  made  by 
the  home  battery  on  the  home  relay  and  is  the  result  of  a  surplus  of  current 
in  the  artificial-line  coil  of  the  relay  over  what  may  be  in  the  main-line  coil. 

AVhen,  due  to  electrostatic  charge  or  discharge  of  the  main  line,  the  current 
in  the  main-line  coil  of  the  relay  is  augmented  above  that  traversing  the 
artificial-line  coil  of  the  relay,  a  false  signal  will  be  produced  unless  at  that 
instant  the  current  flowing  in  tlie  artificial-line  side  of  the  relay  is  increased 
to  an  equal  value.  This  is  what  is  accomplishe<l  by  using  condensers  and  re- 
tardation resistance  coils  in  connection  with  the  artificial  line. 

DOUBLE-CXJREENT    DUPLEX    SYSTEMS. 

As  a  result  of  the  development  of  more  efficient  and  satisfactory  duplex 
systems,  the  single-current  duplex  is  rarely  used  in  this  country,  except  where 
it  is  combined  with  the  polar  duplex  in  forming  the  differential  quadruplex 
system  of  telegraphy  by  means  of  which  two  messages  are  sent  in  each  di- 
rection over  a  single  wire  simultaneously. 

THE  POLAR  DUPLEX. 

The  essential  elements  of  the  polar  duplex  are  a  battery  pole  changer,  a 
differentially  wound  polarized  relay,  an  artificial  line  rheostat,  and  an  arti- 
ficial capacity. 

THE   POLE   rilAXCEU. 

The  transmitter  sliown  in  connection  with  the  single-current  duplex,  figure 
2-17,  has  connected  to  one  of  its  contacts  the  positive  pole  of  a  main-line 
battery  and  to  the  other  contact  a  circuit  to  ground.  If  to  the  latter  the 
negative  pole  of  a  main-line  battery  were  connected  instead  of  the  ground 
wire,  closing  the  signaling  key  would  send  to  line  a  positive  impulse,  and 
opening  the  key  would  send  to  line  a  negative  impulse,  in  which  case  the  trans- 
mitter might  correctly  l)e  regarded  as  serving  as  a  pole  changer,  inasnuich  as 
the  polarity  of  the  battery  placed  in  contact  with  the  line  wire  changes  from 
positive  to  negative  and  vice  versa  each  time  the  transmitter  tongue  is  cau.sed 
to  break  contact  with  the  positive  battery  terminal  and  make  contact  with 
tlie  negative  battery  terminal. 

The  introduction  of  the  double-c-urrent  duplex  t-alled  for  the  substitution  of 
a  transmitter  in  place  of  tlie  type  of  instrument  used  with  the  single-current 
dui)Iex,  which  would   meet  the  changed  conditions. 

'I'lie  new  form  of  transmitter,  or  pole  changer  as  it  has  sinci'  been  termed, 
provides  ff)r  tlie  maintenance  of  an  air  gap,  as  11i(>  iiiiiin-linc  contact  is  shifted 
from  one  iK)le  of  the  battery  to  the  other. 

So  far  as  the  pohir  duplex  is  concerned,  the  saiiie  necessity  does  not  exist  for 
the  employment  of  a  coriliiiuity  pre.serving  transiiiilter  as  was  the  case  with 
the  single-current  duplex,  the  reason  for  which   will   be  explained. 

(50) 


Telegraphy  and  the  Induction  Telegraph  Set. — Chapter  2. 


10 


THK    I'OI.AK    RELAY. 

All  of  tlic  iiiluM-('ii(  riillicultics  cxiHTifiiccd  in  tlu*  ((]H'i-:ili<»ii  of  siii;ile  Mor.se 
lines  are  encoiintcrcil  in  ilic  oiicrai  imi  nl'  ilic  siii;il('-(iirr('iil  liinVi-fulial  liiiplex 
system. 

Duriiif^  favorable  weather  and  where  a  hif^h  degree  of  line  in.siilatioii  is 
maintained  both  of  these  methods  of  telegraphy  are  satisfactory.  But  when, 
due  to  excessive  lealcage  conductance,  the  current  values  at  tlie  receiving  end 
are  low,  considerable  difliculty  is  experienced  in  maintaining  satisfactory 
operation. 

The  polar  chiplex  overcomes  this  difliculty  to  a  great  extent,  and  by  means 
of  this  system  lines  may  be  worked  satisfactorily  long  after  adverse  weather 
conditions  have  rendered  single  Morse  and  single-current  duplex  systems  in- 
operative. 

Figxire  2-20  shows  a  theon'tical  view  uf  tlie  magnetic  circuit  of  the  polar 
relay. 


Arttflinc 


Artif.line 


Fig.  2-20.— TELEGRAPHY,   DUPLEX,   POLARIZED   RELAY,  THEORETICAL  CONNECTIONS. 

It  will  be  .seen  that  the  windings  are  identical  with  those  of  the  ordinary 
single-current  differential  relay.  Current  from  the  battery  flows  through  ilie 
windings  in  opposite  directions,  the  action  of  one  coil  neutralizing  that  of 
the  other,  the  result  of  which  is  that  the  core  is  not  magnetized  so  far  as 
any  action  due  to  the  cun*ent  from  the  battery  is  concerned. 

The  fundamental  difference  between  the  two  instruments  is  that  in  the 
polar  relay  the  tongue  is  held  on  either  side,  due  to  the  magnetic  pull  of  the 
permanent  magnet  which  constitutes  the  cores  of  the  electromagnets. 

In  the  case  of  the  common  differential  relay,  the  armature  tongue  is  held 
in  the  closed  position  by  the  action  of  either  or  both  magnet  colls  and  in  the 
open  position  by  a  spiral  spring.  With  the  polar  relay  the  armature  is  drawn 
into  contact  with  one  or  the  other  poles,  due  to  magnetism  in  the  cores,  result- 
ing from  the  action  of  current  in  either  coil  of  the  instrument.  The  im- 
portant feature  with  the  latter  relay  is  that  after  the  armature  has  once  l>een 
attracted  toward  either  contact  it  will  remain  there,  whether  current  remains 
in  the  coil  winding  or  not  (provided  there  is  no  current  in  the  opposite  coil). 

Referring  to  flgure  2-20:  When  the  key  is  operated,  the  armature  lever  of 
the  pole  changer  is  caused  to  make  contact,  first,  with  the  negative  ix)le  terminal 
and  then  with  the  positive  pole  terminal.  If  the  ohmic  resistances  of  the  real 
line  and  the  artificial  line  are  equal,  current  from  wliichever  dynamo  is  con- 
nected with  the  armature  lever  will  flow  through  the  companion  windings  of  the 


(51) 


20 


Signal  Corps  Manual  No.  3. — Chapter  2. 


relay  differentially,  with  the  result  that  there  is  no  electromagnetism  produced 
in  the  cores  facing  the  relay  armature.  It  matters  not  whether  the  outgoing 
current  is  from  a  positive  source  or  from  a  negative  source,  owing  to  the  fact 
that  it  passes  through  the  windings  of  the  relay  dilTerentially  there  will  be  no 
magnetism  produ^CTl,  and  this  irrespective  of  the  polarity  of  the  current 
flowing  in  the  circuit. 

If  the  key  is  manipulated,  there  will  be  sent  out  a  series  of  impulses  alternat- 
ing in  sign,  from  positive  to  negative  each  time  the  key  is  closed  and  opened, 
and  if  the  resistance  of  the  artificial  line  side  of  the  relay  balances  that  of 
the  line  side,  the  armature  of  the  relay  will  not  be  affected.  Moreover,  it  will 
be  found  that  if  the  relay  tongue  is  moved  by  hand  into  contact  with  its  closed 
contact  or  with  its  open  contact,  it  will  still  remain  passive  to  the  outgoing 
reversals  from  the  i)ole  changer. 

The  magnets  of  polar  relays  are  so  wound  that  when  current  from  the  distant 
station  flows  through  the  main-line  coil,  it  is  given  a  path  through  an  auxiliary 
winding  in  the  opposite  coil  in  the  reverse  direction  which  results  in  the  perma- 
nent-induced magnetism  in  one  of  the  cores  being  neutralized,  while  the  magnet- 
ism existing  in  the  other  core  is  intensified,  causing  the  armature  to  be  attracted 


Fig.  2-21.— TELEGRAPHY,    DUPLEX,    POLAR,    CIRCUITS. 

toward  the  opposite  contact.  The  reverse  action  takes  pjace  when  the  battery 
poles  at  the  home  station  and  at  the  distant  station  are  in  opposition  (like 
poles  to  line)  in  which  case  the  artificial-line  coil  of  the  home  relay  has  its 
magneti.sm  increa.sed,  and  the  line  coil  has  its  magnetism  neutralized.  Tluis, 
due  to  the  action  of  the  current  in  the  coils,  the  armature  is  caused  to  move 
into  contact  with  tlie  open  or  the  clo.sed  contact  as  desired. 

The  ofiice  of  tlie  auxiliary  winding  in  eacli  case  is  to  act  as  a  "clearing  out" 
agency. 

There  are  several  distinct  types  of  polar  relay  u.sed  by  tlu'  v;iri(»us  telegraph 
administrations,  each  relay  having  its  peculiarities  of  design,  but  the  principle 
upftn  which  all  polar  relays  operate  is  the  same. 

Tlie  ai'tificial  line  rheostat,  and  the  artificial  capacity  used  in  connection  with 
I»olar  duplex  ajjparatus  to  "balance"  (he  resistance  and  capacity  of  the  actual 
line,  an;  the  sanu;  as  those  for  tlie  single-current  duplex. 

Oix'ratirm  of  tlie  point'  (luj)lr.v. — Figure  2-121  shows  llic  connections  of  the 
main-line  and  local  circuits  of  the  ])olar  dujilex. 

Complete  equipment  at  both  ends  of  a  duplexed  circuit  are  shown  so  that  the 
various  operations  may  be  treated  with  regard  to  their  effects  upon  the  appa- 
ratus at  both  ends  of  the  line. 


<52) 


Telegraphy  and  the  Induction  Telegraph  Set. — Chapter  2.  21 

PP  and  PC  are  the  pole  cliiinf^ers  jit  stations  .1  and  li,  respectively,  wliile  PR 
and  PR'  are  the  polar  relays,  K  and  K'  the  .signalin}<  keys,  locally  controlling 
tlie  movements  ol"  the  pole-clianyer  armature  in  each  case. 

The  dynamos,  which  furnish  current  for  the  operation  of  the  main-line  relays, 
are  shown — two  at  each  en<l.  In  ea<-h  case  one  of  the  dynamos  lias  its  positive 
terminal  connected  with  the  back  stop  of  the  pole  changer,  while  the  other 
dynamo  has  its  negative  terminal  connected  with  the  closed  contact  of  the  pole 
changer. 

The  resistance  coils  and  condensers,  which  comiirise  the  artificial  line,  are, 
at  each  end  of  the  main-line  circuit,  marked  AL  and  AL' . 

In  tigure  2-21  the  pole  changers  at  each  end  of  the  line  are  closed;  that  is, 
the  armature  levers  of  the  pole  changers  in  each  case  are  in  contact  with  their 
front  stops,  due  to  the  fact  that  the  signaling  keys  K  and  K'  are  close<l.  This 
places  to  line  at  each  end  a  200-volt  negative  battery.  As  the  liatteries  are  of 
equal  potential,  no  current  will  Ilow"  over  the  main  line.  At  the  instant  both 
pole-changer  armatures  make  contact  with  their  back  stops — thus  placing  oppos- 
ing battery  to  line — the  levers  of  the  polar  relays  at  each  end  are  moved  into 
contact  with  their  back  stops,  thereby  opening  the  local  reading  sounder  circuits 
at  each  end.  At  this  point  it  is  important  to  gain  a  correct  understanding  of 
why  the  armatures  of  the  polar  relays  at  each  terminal  station  are  attracted 
toward  either  contact  when  the  main-line  batteries  at  each  end  of  the  line  are  in 
opposition.  The  explanation  is  tluit  when  the  terminals  of  a  wire  are  at  equal 
potential,  no  current  will  flow  in  the  wire.  Therefore,  when  like  poles  of 
itlentical  potential  are  to  line,  as  in  the  case  before  us,  it  is  apparent  that  the 
terminals  of  the  main-line  wire  are  at  equal  potential.  An  entirely  different 
condition,  however,  exists  with  regard  to  the  artificial  line  at  each  end.  As, 
in  eacli  case,  one  end  of  the  artificial  line  is  connected  with  the  earth  (which  is 
at  zero  potential),  there  is  presented  to  the  outgoing  currents  from  each  station 
a  path  to  ground  via  the  artificial  line  magnet  of  the  polar  relay.  On  each 
occasion,  therefore,  when  like  poles  are  to  line  at  each  end,  current  from  the 
liome  battery  flows  through  the  artificial  line  and  the  armature  of  the  polar 
relay  is  attracted  toward  its  back  stop  if  the  opposing  batteries  are  positive 
and  toward  its  front  stop  if  the  opposing  batteries  are  negative. 

In  order  to  carry  on  transmission  in  both  directions  at  the  same  time  it  is 
necessary  that  the  operator  at  ^1  shall  be  able  to  control  the  movements  of  the 
armature  of  the  relay  at  B  regardless  of  which  pole  of  his  battery  B  has  to 
line.  Also,  that  the  operator  at  B  shall  be  able  to  control  the  movements  of  the 
relay  armature  at  A  regardless  of  which  pole  of  his  battery  ^-1  has  to  line. 

Suppose  the  operator  at  B  should  depress  his  key  (while  the  key  at  .1  is 
open),  thereby  placing  the  tongue  of  this  pole  changer  in  contact  with  the  nega- 
tive pole  of  the  main-line  battery  at  B,  the  result  will  be  that  the  main-line 
coil  of  the  relay  at  .1  will  be  energized  and  its  tongue  attracted  toward  its  cU>sim1 
contact,  thereby  operating  sounder  S. 

It  is  evident,  of  course,  that  current  continues  to  flow  through  the  artificial 
line  coil  of  the  relay  at  .1.  but  owing  to  the  fact  that  the  current  strength  in 
the  main-line  coil  of  the  relay  is  twice  that  in  the  former  and  in  the  opi)osite 
direction,  it  is  plain  that  the  magnetism  in  the  core  of  the  relay  at  .4  is 
reversed,  and  the  armature,  as  a  result  thereof,  moves  into  contact  with  its 
front  stop.  If  what  has  previously  been  statetl  is  true,  the  armature  of  the 
relay  at  B  should  have  remained  passive  to  the  reversal  of  current  sent  out  from 
B  when  the  key  at  B  was  closed.  That  this  is  so  is  apparent,  for,' although  the 
magnetism  in  the  artificial  line  magnet  of  the  relay  at  B  has  now  been  ueu- 

(53) 


22 


Signal  Corps  Manual  No.  3. — Chapter  2. 


tralized,  due  to  the  presence  of  current  in  the  main-line  coil  of  the  relay,  the 
armature  is  held  in  the  open  position  by  the  action  of  the  permanent  magnet  asso- 
ciated therewith.  In  other  words,  nothing  has  happened  so  far  to  cause  the 
armature  of  the  main-line  relay  at  li  to  change  its  position  ;  therefore,  it  remains 
in  the  position  taken  when  last  it  was  caused  to  move  by  a  surplus  of  magnetism 
in  one  coil  over  that  obtaining  in  the  other  magnet  coil.  Similarly,  when  A 
alone  closed  his  signaling  key,  the  relay  at  B  responds,  while  the  relay  at  A 
does  not.  When  the  signaling  keys  at  both  ends  are  depressed,  the  line  currents 
once  more  are  in  opposition,  and,  as  in  this  case,  the  currents  flowing  through 
the  artificial  lines  at  each  end  are  in  the  reverse  direction  of  that  taken  when 
both  keys  were  open,  the  relay  armatures  at  each  end  are  caused  to  move  into 
contact  with  their  front  stops. 

In  effect,  therefore,  when  the  operator  at  A  attempts  to  register  a  "  dot "  on 
the  relay  at  B,  at  the  same  instant  that  the  operator  at  B  intends  to  register 
a  "  dot "  on  the  relay  at  A,  each  station  causes  to  be  produced  in  his  own  relay 
the  signal  intended  to  be  transmitted  from  the  distant  end  of  the  line.  Or, 
the  foregoing  might  be  paraphrased  thus :  The  relay  at  A  will  be  closed 
whenever  the  key  at  B  is  depressed,  regardless  of  whether  A  is  sending  or  idle ; 
and  the  relay  at  B  will  close  whenever  the  key  at  A  is  closed  whether  B  is 
sending  or  idle,  but  in  neither  case  will  the  signals  transmitted  from  either  end 
conflict  with  those  originating  at  the  distant  station. 


Fig.  2-22.— TELEGRAPHY,  DUPLEX,  BATTERY. 


THK    BATTEIIV    DUTLKX. 


Figure  2-22  shows  the  theoretic  connections  of  the  main-lino  inslrunients  u.sed 
to  operate  a  polar  duplex  by  means  of  gravity  battery. 

In  this  duplex  arrangement  the  pole  changer  consi.sts  of  Iwo  double-contact 
relays,  or  transmitters.  The  transinitt(M-s  are  connected  in  series,  that  is,  one 
signaling  key  controls  the  opeT'atinn  of  Ixith  inslrunients,  .so  that  both  arma- 
tures arc  in  the  closed  posilion  at  the  siinie  time,  and  in  the  open  iM)si(i<>n  at 
the  same  lime,  depending  upon  whether  the  key  is  oi)en  or  closed. 

It  will  be  .seen  at  a  glance  that  when  both  artnature  levers  are  in  contact 
with  their  back  stops  the  positive  pole  of  the  row  of  gravity  cells  is  conni'cted 
to  line  via  the  tongue  of  transmitter  No.  1,  and  at  the  same  time  the  negative 
pole  of  the  battery  is  "grounded"  via  the  tongue  of  transmitter  No.  2.  Con- 
versely, when  the  signaling  key  is  closed  mid  holli  tongues  ai-e  against  their 
front  stores,  the  negative  pole  of  llic  hiiltcry  is  connected  to  line  and  the  posi- 
tive terniinal  of  the  battery  (n  grouml.  Tlic  opnnition  of  the  key,  controlling 
as  it  does  simultaneously  the  operation  of  both  transmitters,  residts  in  alter- 
nate positive  and  iK-gativc  impulses  being  sent  to  line,  the  same  as  when  two 
dyrvimos  (»f  oi»posil(>  i»olarities  are  used. 

In  other  resfK'cts  the  r-oiiiiections  are  the  same  iis  in  the  dynamo  jtolar  duplex. 

(r.4) 


Telegraphy  and  the  Induclion  Telegraph  Set. — Chapter  2. 


23 


THK    "  lilllUCK  "    DLI'LEX. 

The  sinRle-ciirrent  duplex  and  tlio  itolar  duplex  l)einK  basetl  <ui  the  differ- 
ential principle  are  dependent  upon  iirodueint;  an  equality  of  current  strengths, 
while  the  bridjie  duplex,  which  is  based  upon  the  well-known  Wheatstone 
bridge  principle,  is  dependent  upon  itroducinj;  an  equality  of  potentials. 

Fifiure  2-23  shows  two  stations  .1  and  Ji  at  either  end  of  a  line  wire  e<iuipi>e<l 
with  bridjie  duplex  apjiaratus. 

li  and  li'  are  tlie  niain-line  batteries  at  .1  and  li  respectively,  .l/y  in  each 
case  represents  the  artificial  line  at  either  end.  li  and  Ji'  are  two  artihcial  re- 
sistances of  equal  value,  likewise  r  and  r'  at  station  B.  At  each  end  of  the 
line  the  relays  are  connected  between  the  points  c  and  d  of  the  "  bridge " 
formed  by  the  line  wire  and  the  artificial  line  resistance.  Closing  the  key  at  .1 
sends  out  a  current  which  divides  at  n,  half  passing  over  the  line  wire  to  .sta- 
tion /{  and  reaching  eartli  via  the  aitjtaratus  at  that  end  of  the  line,  while  the 
other  half  passes  through  the  artiticial  line  at  .1,  reaching  the  earth  at  that  end 
of  the  <-ircuit.     Inasmuch  as  the  points  <■  and  d  are  equidistant,  ohmically,  from 


LINE. 


■m^ 


-Mh 


Fig.  2-23— TELEGRAPHY,    DUPLEX,    BRIDGE,   THEORETICAL  CONNECTIONS. 

the  i)oint  a,  their  potential  values  are  identical,  and  no  current  will  flow 
through  the  windings  of  the  relay  at  ^1.  This  is  true,  of  course,  oidy  when  the 
resistance  of  the  artificial  line  at  A  is  made  equal  to  the  resistance  of  the 
actual  line  to  ground  at  the  distant  end.  The  relay  at  .1.  therefore,  is  not 
affected  when  A  sends  to  B.  The  same  condition  prevails  when  B  alone  sends 
to  A.  Signals  from  A  operate  the  relay  at  B  because  the  incoming  signals  have 
a  joint  path  made  up  of  the  branches  c-d  and  c-a,  thus  .setting  up  a  difference 
of  potential  between  the  points  c  and  d  sufficient  to  operate  the  relay. 

The  operations  which  take  place  with  different  key  combinations  at  «'itlier 
end  of  the  bridge  duplex  may  be  traced  without  difficulty. 

Since  the  line  relay  employed  in  the  bridge  duplex  does  not  need  to  be  differ- 
entially wound,  it  is  evident  that  any  ordinary  relay  may  be  used  with  this 
method  of  duplexing.  It  is  apparent,  also,  that  the  outgoing  currents  do  not 
pass  through  the  windings  of  the  home  relay,  and.  as  the  currents  pa.ss  directly 
to  line,  there  is  a  minimum  amount  of  retardation  in  the  sending  circuit.  And. 
further,  it  is  claimed  for  the  bridge  duplex  that  its  line  relays,  on  account  of 
their  position  in  the  brid.ge,  are  not  as  resjionsive  ti>  induced  line  disturbances 
or  to  earth  currents  as  are  the  line  relays  in  the  dilTer<>ntial  duplex.  This  is 
due  to  th(>  fact  that  in  the  bridgi'  .system  only  a  portion  of  the  line  currents 
pa.ss  through  the  relay,  no  matter  whether  the  currents  are  the  result  of  an 
impressed  e.  m.  f.,  of  induction,  or  of  conduction  from  neighboring  circuits,  while 


(55) 


24  Signal  Corps  Manual  No.  3. — Chapter  2. 

in  the  differential  duplex  all  currents  existins  in  the  main  lin(>  jiass  tliroush 
the  windings  of  the  line  coil  of  the  relay. 

The  bridge  duplex  has  been  more  highly  developed  in  Eiu'ope  than  in  America, 
and  several  of  the  refinements  applied  to  its  operation  there  are  particularly 
noteworthy  as  having  a  bearing  on  the  general  subject  of  high-speed  signaling. 

BALANCING    THE    POLAU   DUPLEX. 

The  polar  duplex  is  balanced  by  asking  the  distant  station  to  "  ground." 
This  he  does  by  throwing  the  3-point  switch  G.S',  figure  2-21,  to  down  position. 
(Sometimes  the  left-hand  lower  "point,"  or  disk,  is  connected  to  the  earth  via 
SC,  sometimes  it  is  the  right-hand  lower  point  that  is  so  connected.)  This 
action  disconnects  the  pole  changer  and  battery  from  the  line  and  transfers  the 
latter  to  the  earth  via  tlie  resistance  coil  8C  or  SC.  These  resistance  coils  ai'e 
inserted,  as  in  the  Stearns  duplex,  to  compensate  for  the  internal  resistance  of 
the  battery  at  each  end.  When  the  distant  switch  has  been  turned  the  home 
switch  is  also  similarly  turned.  The  adjusting  screw  of  the  polarized  relay  is 
turned  forward  or  backward  until  the  armature  remains  on  whichever  side  it 
may  be  placed.  The  home  battery  is  then  placed  to  the  line  by  turning  the 
.switch  OS  to  the  up  position  right.  Then  the  pole  changer  is  opened  and 
closed  and  the  i-esistance  in  AL  or  Afy  is  adjusted  iintil  the  armature  of  the 
relay  remains  on  either  side,  as  before.  This  insures  a  "  resistance  "  balance. 
The  pole  changer  is  now  closed  and  opened  rapidly,  and  if  short  clicks  are  heard 
the  capacity  of  the  condenser  is  varied  until  these  disappear  altogether.  This 
shows  that  a  "  static  "  balance  has  been  obtained.  A  static  balance  can  also 
be  had  by  asking  the  distant  station  to  "  cut  in,"  which  he  does  by  tiu'ning  the 
switch  to  the  up  position.  When  he  has  done  so,  ask  him  to  close  his  key.  so 
that  the  armature  of  the  home  relay  will  rest  against  its  contact  point.  The 
armatiu'e  may  then  be  given  a  slight  bias  awa.v  from  its  contact  point  and  the 
home  pole  changer  again  operated.  If  clicks  are  still  heard  in  the  sounder,  the 
condenser  and  its  resistance  coil  are  adjusted  initil  they  disappear,  when  the 
distant  end  may  be  asked  to  send  a  few  words,  to  give  an  opportunity  to  read- 
just the  armatui'e  to  its  proper  plac-e.  As  a  rule,  however,  a  good  working 
static  balance  can  be  obtained  on  a  polar  duplex  without  giving  the  armature 
of  the  polarized  relay  a  bias. 

Western  Union  1'ole  Changer. 

The  Western  Union  standard  pole  changer  for  gravity  batteries  is  shown  in 
figure  2-24.  The  contact  points  of  the  instrument  are  inclosed  in  a  circular 
glass-incased  box.  The  end  of  the  lover  L  is  seen  extending  into  the  box 
through  an  aperture  in  the  back  of  the  framework.  The  tension  springs  K  S' 
are  insulated  from  the  box.  The  contacts  C  C  are  attached  to  the  framework. 
The  poles  of  the  battery  are  generally  connected  to  the  springs  S  fi'  by  way 
of  their  respective  binding  posts  on  the  side  of  the  baseboard.  The  lever  is 
connected  to  the  earth,  and  the  contact  points  C  C  to  the  line,  or  vice  versa, 
as  desired;  also  via  the  binding  posts. 

TllK     \l>.irST.Mi:.\T    OK    TELEfiKAI'H    APPARATUS.' 

If  operators  in  general  could  be  nL'idc  to  realize  bow  nnicii  more  comfort 
they  might  take  in  their  daily  work  did  they  but  ac(|uii'('  even  a  slight  knowl- 
edge of  the  knack  of  adjusting  their  instruments  i)r(»i)erly,  they  would  certainly 

1  By  Willis  n.  Jones,  in  tbe  Telcgrapii  Age,  September  and  October,  1902. 

(56) 


Telegraphy  and  the  Induction  Telegraph  Set. — Chapter  2. 


25 


make  a  move  in  that  direction   t'<ir  tlieir  own  interest  if  not  for  tiiat  of  the 
company  emphtyins  them. 

Tliere  is  positively  no  excuse  for  tlie  indistinct  manner  in  winch  si^rnals 
are  so  frequently  recorded  on  the  really  lirst-cla.ss  instruments  employi'<l  by 
telegraph  companies  to-day.  When  the  sijrnals  do  not  arrive  in  proper  shape 
there"  is  some  good  reason  for  it,  but  the  theory  of  the  fault  given  by  the 
average  operator  is  nsually  wide  of  the  mark,  and  as  he  "adjusts"  in  ac- 
cordance with  his  ideas  of  the  trouble,  he  generally  makes  matters  worse  by 
such  eltorts. 


Fig.  2-24.— TELEGRAPHY,    DUPLEX,   POLE  CHANGER. 

For  tlie  purpose  of  demonstration  let  lis  see  wliat  may  be  learned  in  the  way 
of  adjustment  and  care  of  an  ordinary  single-line  relay  and  sounder.  Now, 
we  will  assume  that  the  wire,  battery,  and  instrument  coils  are  in  first-class 
order  and  then  introduce  a  few  conditions  for  the  pui'pose  of  noting  the 
different  effects  produced  on  the  apparatus. 

Wet-Weatheu  Effects. 

In  wet  weather  the  quantity  of  current  which  traverses  the  coils  of  a  relay 
is  greatly  increased  at  or  near  the  battery  station  over  and  above  that  which 
normally  flows  in  clear  weather,  while  distant-station  instruments  receive  less 
than  the  usual  amount.  This  condition  is  caused  by  the  numerous  •' e.scai)es  " 
or  side  paths  down  the  poles  along  the  route  which  draw  additional  current 
from  the  dynamo,  all  of  which  must  necessarily  pass  through  the  relays  in- 
serted between  them  and  the  battery.  Distant  relays  receive  less  than  they 
are  entitled  to,  because  much  of  the  current  on  the  wire  "  escapes "  down 
the  wet  poles  before  reaching  them.  Now,  a  strong  current  in  the  coils  means 
a  strong  magnetic  pull  on  the  relay  armature,  while  a  weak  current,  of  course, 
causes  a  correspondingly  weak  attraction. 

It  follows  from  this  that  the  wet-weather  method  of  adjusting  a  distant 
relay  is  directly  opposite  to  that  followed  for  the  home  relay  at  the  battery 
end  of  the  circuit.     The  operators  at  distant  points  must  get  the  magnets  closer 

(57) 


26  Signal  Corps  Manual  No.  3. — Chapter  2. 

and  closer  to  the  armature  as  the  downfall  of  rain  increases,  while  the  home 
operator  is  compelled  to  draw  his  relay  coils  away  from  it.  This  seems  like 
a  very  simple  operation  to  perform,  but  the  maniier  in  which  most  operators 
go  about  it  explains  why  they  fail  to  secure  the  best  residts. 

The  first  principle  of  adjustment  lies  in  maintaining  at  all  times,  whether 
the  current  is  weak  or  strong,  a  praictically  constant  or  normal  tension  of 
the  retractile  spring  attached  to  the  relay  armature.  The  explanation  is 
that  a  relay  spring  responds  best  to  the  magnetic  attraction  of  the  armature 
when  the  tension  is  such  that  the  "  curling "  is  not  stretched  to  any  great 
extent  out  of  its  original  close-fitting  construction  when  new. 

The  adjustment  should  invariably  be  made  by  moving  the  magnet  backward 
or  forward  by  means  of  the  thumbscrew.  The  tension  of  the  retractile  spring 
need  not  be  altered  perceptibly  except  to  give  the  operation  a  finishing  touch. 
The  habit  of  stretching  the  relay  spring  to  meet  a  strong  magnetic  pull  not 
only  causes  the  former  to  work  less  efficiently  at  the  time,  but  soon  injures 
it  permanently  by  destroying  its  sensitiveness. 

Feeling  for  a  Distant  Station. 

It  frequently  happens  in  very  wet  weather  that  a  distant  office  can  not 
"  break  "  the  operator  at  or  near  the  battery  station  on  account  of  the  difficulty 
the  latter  has  in  getting  a  fine  adjustment.  When  informed  via  some  othert  cir- 
cuit that  such  is  the  case  the  best  method  to  pursue  is  as  follows :  IMake  a 
few  dots  to  attract  his  attention  (he  will  hear  you;  the  distant  office  has  the 
advantage  in  this  respect)  and  then  tell  him  to  "dot."  Now  pull  the  magnets 
back  from  the  relaj'  armature  until  the  circuit  stands  apparently  just  open. 
Next  turn  down  the  retractile  spring  very  slowly  until  you  hear  the  signals. 
If  you  miss  them,  you  may  sometimes  catch  them  by  placing  your  finger  on 
the  lever  of  the  relay  and  giving  it  a  gentle  pressure  back  and  forth.  If  the 
operator  is  dotting,  you  will  feel  the  impulses  and  thus  be  able  to  readjust  the 
Instrument. 

The  latter  metliod  is  an  excellent  one  to  pursue  on  a  way  wire  when  in  doubt 
as  to  whether  anyone  is  using  the  circuit,  for  by  this  precaution  one  operator 
need  never  break  in  while  another  is  sending.  However,  as  it  is  only  in  very 
wet  weather  that  an  operator  is  bothered  to  any  great  extent  by  the  relay,  the 
real  source  of  daily  discomfiture  usually  lies  in  an  improper  adjustmnet  of 
the  sounder. 

ad.tttstment  ok  sounders. 

When  a  sounder  does  not  give  out  a  loud  enough  tone  to  suit  an  operator,  he 
almost  invarial)ly  proceeds  to  give  the  lever  a  wider  play,  as  if  that  was  the 
only  remedy.  As  a  matter  of  fact  that  process  in  itself  seldom  brings  about 
the  desired  results  unless  the  lever  at  the  time  happens  to  lie  screwed  down 
abnormally  close.  The  important  thing  to  know  is  that  if  you  give  the  lever  a 
play  which  will  permit  the  armature  to  move  away  from  the  magnet  cores 
beyond  a  normal  distance,  the  magnet  lias  a  hard  time  getting  control  of  it 
again.  The  explanation  is  that  a  magnet  loses  its  power  to  attract  the  armature 
in  a  degree  directly  jtroportional  to  tlie  square  of  the  distance  separating  them; 
or,  in  other  words,  to  the  square  of  the  air  gap.  For  example,  if  two  magnets 
similarly  constructed  in  all  respects  be  f(>(l  by  an  ecpial  strength  of  currcMit,  and 
tlH'  air  gap  between  the  cores  .hhI  the  :iiiiiature  of  one  miule  the  thickness  of  a 
cardboard,  while  two  cards  could  occuiiy  the  gap  in  the  second  magnet,  the 
former  would  be  practically   four  times  as  strong  as  tli(>  latter.     It  is  plain, 

(58^ 


Telegraphy  and  the  Induction  Telegraph  Set. — Chapter  2.  27 

therefore,  that  to  give  the  sounder  lever  too  great  a  i)hi,v  will  so  weaken  the 
pull  on  the  armature  when  in  its  "  opi-n  "  position  tliat  when  tiie  local  circuit  is 
again  closed  the  lever  moves  so  shnvly  at  first  that  it  hardly  has  time  to  cross 
over  the  space  hefore  the  current  is  again  hroken.  The  result  is  that  a  signal 
is  partially  broken  up  before  completion. 

The  lesson  to  be  learned  from  this  is  that  the  play  given  to  an  armature 
lever  must  never  l)e  so  great  that  the  magnet  can  not  bring  it  back  promptly 
within  the  time  allotted  to  complete  a  signal.  This,  in  turn,  sugge.sts  that  the 
amount  of  play  given  should  be  decrea.sed  in  proportion  to  the  speed  with  which 
the  signals  are  increased.  The  proper  method  to  increase  the  volume  of  sound 
is  as  follows : 

AI).Il'STIN(;    lOK    M.WI.MIWL    STKENtJTII. 

IMace  a  sheet  of  i)aiier  between  tlie  aiMiialure  and  tlii'  poles  of  llie  sduuder 
magnet  and  tiien  lower  the  former  until  there  is  just  space  enough  to  move  the 
paper  back  and  forth  without  catching.  This  permits  the  magnet  to  exert  its 
maximum  strength  on  the  lever,  and  the  position  should  seldom  be  altered. 
Whatever  changes  are  necessary  during  the  process  of  adjusting  should  be 
effected  by  means  of  the  spring,  the  upi)er  thumbscrew,  and  those  which  regu- 
late the  trunnion.  The  adjustment  of  the  trunnion  screws  is  a  matter  too 
generally  overlooked.  It  is  there  that  the  pitch  or  quality  of  the  sound  is  regu- 
lated.    The  pivot  nuist  not  bind  too  tightly,  nor  yet  be  too  loo.se. 

When  signals  do  not  reach  the  operator  in  the  particular  style  that  suits  his 
fancy,  he  usually  atteini)ls  (o  remedy  the  fault  by  giving  the  sounder  lever  a 
greater  or  a  lesser  jilay.  If  the  trouble  happens  to  lie  in  an  improper  adjust- 
ment of  that  part  of  the  apparatus  he  may  possibly  succeed  in  helping  matters, 
but  the  fact  is  that  indistinct  signals  may  be  due  to  a  great  variety  of  causes, 
any  one  of  which,  in  his  ignorance,  he  may  never  suspect. 

For  the  purpose  of  illustration,  let  us  again  take  the  ca.^e  of  an  ordinary 
single-line  relay  and  sounder  and  assume  that  despite  a  careful  adju.strnent  of 
th(>  relay  and  sounder  magnets  after  the  manner  suggested  in  the  prece<ling 
installment  of  this  article  th«i  signals  continue  to  "drop  out"  at  times. 

The  lirst  thing  to  determine  is  whether  the  fault  lies  in  the  relay  or  the 
sounder.  Such  disturbances  are  usually  due  to  a  loose  or  improper  connection 
somewiiere  in  the  local  circuit,  but  not  alwa\s.  Naturally  the  first  move  made 
toward  locating  the  trouble  should  be  to  examine  all  binding  posts,  and  opera- 
tors in  general  would  save  themselves  many  annoyances  if  they  would  acquire 
the  habit  of  doing  this  whenever  they  sit  down  to  a  different  set  of  instruments. 
If  the  binding-post  connections  prove  to  be  secure,  open  the  key  and  "dot"  or 
"write"  with  your  hnger  on  the  relay  armature  or  lever,  using  the  latter  as  a 
key.  If  the  signals  then  respond  firmly  and  distinct,  the  local  circuit  is  not 
fauhy,  and  attention  should  be  directed  to  the  relay. 

In  many  cases  the  source  of  the  trouble  will  turn  out  to  be  too  tight  an  adjust- 
ment of  the  trunnion  binding  posts,  thus  preventing  the  restrained  armature 
from  responding  readily  to  the  influence  of  the  magnet.  This  fault  is  particu- 
larly applicable  to  circuits  in  which  the  strength  of  the  current  flowing  through 
the  relay  coils  is  weak.  Where  the  main-line  current  is  strong,  the  magnet  is 
frequently  able  to  overcome  this  drawback,  but  it  is  evident  that  even  then  tlie 
working  margin  of  that  instrument  has  been  cut  down  to  the  extent  that  the 
trunnion  binds.  It  follows,  then,  that  the  trunnion  binding  posts  should  always 
be  so  adjusted  that  the  crossbar  or  axis  upon  which  the  lever  and  armature 
rests  may  move  jterfectly  free  in  its  .sockets. 

46581°— 17 5  (59) 


28  Signal  Corps  Manual  No.  3. — Chapter  2. 

If,  hoA\ever,  the  signals  made  in  the  manner  suggested  continue  to  drop  out 
despite  tliis  precaution,  the  fault  will  possibly  be  found  in  a  loose  connection 
somewhere  in  the  local  circuit.  If  tightening  the  binding  posts  fails  to  remove 
the  trouble,  examine  the  fine  wire  wound  around  the  shaft  of  the  relay  lever, 
one  end  of  which  is  attached  to  the  shaft  and  the  other  to  a  part  of  that  trun- 
nion binding  post  where  the  local  battery  makes  its  exit.  If  this  wire  becomes 
broken,  the  sounder  signals  will  certainly  "drop  out"  at  times  owing  to  the 
loose  connection  made  between  the  shaft  and  the  post  as  the  former  turns  in 
the  socket.  The  purpose  of  the  fine  wire  is  to  bridge  over  this  unavoidable  break 
in  the  local  circuit,  and  the  operator  will  at  once  see  the  necessity  of  keeping 
that  connection  intact. 

When  a  sounder  stands  "open"  and  it  is  desired  to  ascertain  if  the  break  in 
the  local  circuit  lies  in  some  of  the  relay  connections,  place  the  blade  of  a  knife 
across  both  local  binding  posts  (situated  just  behind  the  relay  spring).  If 
the  opening  is  in  that  instrument,  the  sounder  will  then  close.  If  the  latter 
remains  open,  try  the  same  method  with  the  two  posts  of  the  sounder  itself. 
If  the  coil  or  wire  connections  there  are  broken,  a  si)ark  will  be  noticed  the 
moment  the  blade  makes  and  breaks  contact  ^^•ith  the  two  posts.  The  sounder, 
however,  will  not  close,  because  the  magnet  coils  are  cut  out. 

The  knife-blade  method,  however,  should  never  be  resorted  to  where  sounders 
are  connected  up  in  multiple,  such  as  is  usually  the  case  in  our  large  modernly 
equipped  offices,  because  the  cutting  out  of  the  coil  draws  so  much  current 
through  the  low-resistance  route  via  the  blade  that  it  melts  the  fuse  and  opens 
the  other  four  or  five  companion  sounders  comprised  in  that  particular  group. 
Ojjorators  see  this  fact  frequently  demonstrated  in  large  telegraph  oftices 
when  someone  thoughtlessly  or  ignorantly  permits  a  steel  penholder  or  other 
piece  of  metal  to  sinuiltaneously  make  contact  with  both  binding  posts  of  the 
sounder  or  resonator  connections.  When  this  occurs,  the  "locals"  go  off  on 
several  adjacent  desks  and  business  is  suspended  imtil  a  new  fuse  is  substi- 
tuted. The  blade  may  be  placed  across  the  local  posts  of  the  relay,  however, 
because  it  will  not  cut  out  the  coils  of  the  magnet,  hence  the  resistance  is  not 
lowered.  It  may  also  be  done  where  the  sounder  (Toils  are  in  series  with  a  loop 
or  lamp  resistance,  such  as  the  arrangement  which  obtains  with  duplex  and 
quadruplex  circuits. 

It  will  be  seen  from  what  has  been  stated  that  the  adjustment  and  un- 
derstanding of  even  an  ordinary  relay  and  sounder  require  considerable  skill 
and  a  fair  degree  of  electrical  knowledge,  yet  an  operator  who  does  not  possess 
ambition  enough  to  interest  himself  to  the  extent  of  understanding  the  instru- 
ment before  him  certainly  deserves  much  of  the  needless  provocations  which 
come  his  way. 

Up  to  this  point  the  suggestions  concerning  various  methods  of  adjusting 
telegraph  apparatus  have  been  confine<l  to  the  receiving  instruments.  Tlie 
sending  apparatus,  however,  demands  quite  as  nuich  attention  and  skill  on  the 
I)art  of  the  operator  as  the  receiving  instruments. 

Operators,  as  a  rule,  hardly  realize  the  fact  that  with  but  a  very  little  study 
on  their  part  it  lies  within  their  power  to  not  only  make  their  own  work  much 
easier,  but  that  also  of  tiie  niiin  at  the  distant  end  of  the  circuit. 

One  of  the  most  connnon  iiiis(Ml<('s  the  oi)erator  makes  is  to  find  fault  with  the 
key  frequently  because  of  his  inability  to  send  fast  or  to  make  the  Morse  alpha- 
bet easily.  It  may  surprise  many  readers  to  learn  that  as  a  matter  of  fact  the 
key  is  seldom  to  blame.  It  is  really  a  matter  of  what  is  called  the  electrical 
an>l  the  niechanifiil  inertia  of  the  instruments  that  cause  the  trouble. 

(60) 


Telegraphy  and  the  Inductiun  Telegraph  Set. — Chapter  2.  29 

For  example:  In  ji  telejrraiili  wire  where  tlien-  arc  a  jxreat  many  otlices  close 
together,  such  as  we  tind  on  some  railroad  circuits,  there  are  necessarily  many 
relays,  the  highly  wound  coils  of  which  compose  the  greater  part  of  the  total 
resistance.  Where  such  a  condition  exists  the  counter  electromotive  force 
developed  within  and  by  the  coils  is  so  great  that  it  checks  the  quick  action  of 
the  current  in  its  operation  of  building  up  the  magnetism  in  the  iron  cores  of 
the  relays,  and  thus  deniands  a  slower  rate  of  speetl  on  the  part  of  the  sending 
operator  in  tirder  to  fully  form  his  characters.  Unless  ho  complies  with  this  law 
the  second  impluse  in  the  formation  of  a  character  will  be  begun  before  the 
preceding  one  has  been  fully  "  built  up,"  with  the  result  that  the  key  will 
"  stick,"  as  he  erroneously  believes,  and  the  key  gets  the  blame. 

With  sounders,  as  usually  arranged,  the  case  is  different,  but  the  effect  is 
just  the  same.  If  you  give  the  lever  of  a  sounder  an  abnormally  great  degree  of 
play,  and  then  make  "  dots  "  exceedingly  rapid,  the  lever  will  probably  remain 
in  an  "  open  "  position  during  the  experiment.  Decrea.se  the  speed  somewhat 
and  it  will  respond  iudilYerently.  If,  however,  you  open  and  close  the  key  very 
slowly,  the  Uwer  will  follow  the  movement  faithfully.  Finally,  if  you  adjust 
the  lever  armature  close  to  the  magnet  and  give  it  l)ut  very  little  play,  every 
"  dot "  will  be  heard,  no  matter  how  fast  you  make  them. 

The  lesson  to  be  learned  from  these  experiments  is  that  where  speed  is  re- 
quired the  lever  must  be  given  as  little  play  as  practicable  in  order  to  reduce 
the  mechanical  inertia  to  a  minimum.  Where  an  operator  ignores  this  rule, 
in  order  to  get  a  greater  volume  of  sound  to  receive  by,  he  will  experience  the 
.same  dilliculty  in  forming  the  alphabet  as  his  friend  with  the  choked  relay  did, 
and  probably  vie  with  him  in  condemning  the  greatly  abused  key. 

The  application  of  these  lessons  is  directed  principally  to  those  in  charge  of 
duplex  and  quadruplex  apparatus,  and  cautionary  to  operators  in  branch  offices 
working  sounilers  on  legs  or  loop  extension.  On  account  of  the  tongue  and  the 
retractile  spring  on  transmitters,  and  the  accuracy  with  which  pole  changers 
must  be  manipulated,  those  instruments  demand  very  careful  adjustment  to 
the  speed  of  the  transmitting  operator.  Sounders,  on  the  other  hand,  once 
properly  adjusted,  respond  so  clearly  (on  the  transmitting  side)  that  operators 
in  branch  offices  working  on  duplex  loops  find  that  the  sending  side  works, 
apparently,  as  well  on  a  poor  wire  as  a  good  one.  The  result  is  that  in  bad 
weather  the  fact  is  frtniuently  overlooked  that  the  pole  changer  or  transmitter, 
as  the  case  may  be,  can  not  perform  their  functions  properly  at  a  dry-weather 
speed,  and  thus  by  maintaining  their  usual  speed  cause  no  end  of  trouble  both 
to  themselves  and  the  quadruplex  chief  at  the  main  office. 

PowEii  i-OK  Operating  Telegraph   Systems. 

Most  of  the  large  telegraph  systems  are  operated  by  current  obtained  direct 
from  generators  driven  by  electric  motors. 

Where  batteries  are  used  for  operating  telegi-aph  systems,  they  are  fre- 
quently of  high  voltage,  and  particular  attention  shouhl  be  given  to  insure  of 
their  being  highly  insulated. 

With  storage  batteries  for  this  purpose,  if  the  small  porcelain  or  gla.ss  in- 
sidators  for  each  cell  are  furnished  so  much  the  better;  if  not,  the  shelves 
i^hould  be  as  well  insulated  as  possible,  or  strips  of  glass  or  small  strips  of 
paraffined  wood  under  each  cell  may  be  used  in  an  emergency. 

In  charging  some  of  the  smaller  types  of  cells  a  convenient  arrangement 
is  represented  in  figures  2-2.")  and  2-26.  In  this  the  electric-light  mains  are  con- 
nected with  the  storage  cells  with  some   incandescent  lamps   in  parallel,   as 

(61) 


30 


Signal  Corps  Manual  No.  3. — Chapter  2. 


shown.  If  110-volt  32-can(llepo\ver  carbonized  filament  lamps  are  used,  each 
lanjp  allows  approximately  1  ampere  of  current  to  pass.  So  with  a  type  of 
cell  requiring  6  amperes,  6  lamps  in  parallel  would  permit  the  required  cur- 


£/ectr/c  Ught  Leads 


Lamps 


'M 


Storage  Cef/s 


Fig.  2-25.— TELEGRAPHY,    POWER,    CHARGING    STORAGE    BATTERY. 

rents  to  pa.ss.     Of  course  the  source  of  supply  must  be  a  direct,  not  an  alter- 
nating, current. 

The   diagrams    (figs.   2-2.'i   and   2-2G)    show   the   arrangement    for   an    odice 
where  a  constant-current  lighting  current  is  available  as  a  supply. 


Electric  Light  Mains 


Lamps 


SM 


Storarfe 


ISJ 
•Cell 


f^  I    Relays  and 
Sounders 


Fig.  2-26.— TELEGRAPHY,    POWER,   CURRENT    FOR    RELAYS   AND   SOUNDERS. 

The  lamps  may  be  used  to  illuminate  the  office,  as  the  opposing  E.  IVI.  F.  of  the 
one-storage  cell  (fig.  2-26)  will  not  perceptibly  diminish  their  light.  As  will  be 
noted,  the  storage  cell  is  constantly  in  use  even  while  charging. 

0)n  account  of  its  low  internal  resistance,  as  many  sounder  circuits  in 
parallel  can  be  fed  from  one  of  these  storage  cells  as  the  capacity  of  the 
battery  will  permit.  Each  sounder  requires  one-fourth  ampere,  so  in  24  hours 
it  would  require  at  most  6  ampere  hours  to  supply  it.  And  if  the  storage 
cell  had  a  capacity  of  50  ampere  hours  it  could  supply  four  sounder  circuits 
24  hours  and  still  hav(>  a  reserve  foi-  another  day  in  case  of  accident  to  the 
charging  circuit. 

Induction  TKi.KoitAiMi  Skt. 

The  induction  tch'gra|)li  set  (tig.  2-27)  is  strictly  a  iiortable  field  instnunent 
which  was  devei()|»ed  by  the  Signal  ('orjjs.  It  is  designed  for  sending  Morse 
signals  over  field  lines  of  connnunication  and  other  lines  where  it  is  diflicult 


(C2) 


Telegraphy  and  the  Induction  Telegraph  Set.— Chapter  2.  31 


Binding  posts,  complete 

Case,  complete 

Case,  cover  for 

Case,  hinge  for 

Case,  circuit  diagram  frame 

Case,  circuit  diagram 

Case,  circuit  diagram,  celluloid  cover  for 

Case,  cover  fastener,  complete 

Case,  internal,  for  battery 

Battery,  timgsten,  t\"pe  A  (2  units  to  a  set) 

BatterV,  spring  and  support  for 

Switch",  D.  P.  I).  T..  complete 

Switch,  D.  P.  D.  T.,  handle  for 

Key,  complete 

Key,  spring  for 

Key,  spring  adjust  ing  screw , 

Key,  roar  adjusting  screw 

Key,  trumiion  screw  and  lock  nut 

Key,  handle  for 

Sounder,  complete 

Sounder  base 


Sounder  armature. 

Sounder  armat  ure  supports ;  — 

Soimder  permanent  magnet 

Sounder,  coils  for  (2  to  a  set) 

Sounder,  armature  movement  adjusting  screw. 

Sounder  spring  tension  adjusting  screw 

Induction  coil,  complete 

Induction  coil,  coil  for  (2  to  a  set) 


(63) 


32 


Signal  Corps  Manual  No.  3. — Chapter  2. 


to  supply  the  large  amount  of  battery  required  for  ordinary  telegraphic  work. 
It  can  also  be  used  for  the  transmission  of  speech  by  making  certain  moditica- 
tions.  The  instrument  comprises  a  wooden  case  the  dimensions  of  whicli  are  11^ 
by  75  by  6  inches,  outside.  The  top  of  the  case  contains  instructions  for  op- 
erating and  a  diagram  of  circuits.  A  baseboard,  which  is  removable  by  means  of 
four  screws,  has  on  its  underside  the  wiring  and  has  on  its  upper  surface  a  bat- 
tery case  of  aluminum  to  hold  two  tungsten  batteries ;  an  induction  coil  of  the 
closed  magnetic  circuit  type ;  a  doul)le  contact  telegraph  key  of  standard  pat- 
tern ;  a  polarized  sounder,  which  will  be  described  later ;  a  double-pole  double- 
throw  switch  for  reversing  the  connections  to  line,  and  three  binding  posts  num- 
bered 1,  2,  and  3.  In  addition,  authority  has  beeu  issued  by  the  Chief  Signal 
Officer  to  install  a  fourth  binding  post  on  all  instruments  in  service,  to  be  con- 
nected to  the  contact  of  the  bottom  battery.  This  is  for  the  purpose  of  at- 
taching external  battery  to  this  instrument  and  for  this  purpose  the  batteries 
in  the  case  must  be  removed  and  external  battery  connected  to  binding  posts 
3  and  4.  The  line  is  connected  to  binding  posts  1  and  2  as  usual.  This  set 
can  be  used  for  ordinary  Morse  telegraphy,  in  which  case  the  line  is  connected 
to  binding  posts  2  and  3,  and  the  small  blocking  screw  which  prevents  the 
switch  of  the  key  from  being  closed  should  be  run  down  with  a  screw  driver  so 
that  the  switch  may  be  kept  normally  closed  when  not  sending. 

Previous  models  of  the  field  induction  telegraph  set  used  a  polarized  relay 
of  a  well-known  connnercial   form   and,   in  addition,   required  a  local  battery 


=^«CY 


BATTEIRY 


Fig.  2-28.— TELEGRAPH     INDUCTION    SET,  THEORY    OF    OPERATION. 

and  local  sounder  to  be  connected  to  the  relay  tongue.  The  model  1912  set 
contains  what  is  known  as  a  "  polarized  sounder."  It  consists  of  a  I'egular  local 
sounder  frame,  underneath  which  is  mounted  a  strong  permanent  magnet,  the 
cores  of  the  coil  forming  the  pole  pieces  of  the  magnet.  The  coils  are  so  wound 
that  a  current  in  one  direction  tends  to  increase  the  strength  of  the  magnet  and 
in  the  other  direction  tends  to  decrease  the  strength  of  the  magnet.  The  arma- 
ture is  adjusted  by  means  of  a  .spring  so  that  it  remains  in  either  the  up  or 
down  position  when  no  current  is  flowing.  When  an  instantaneous  current 
comes  over  the  line  due  to  the  depression  of  the  key  at  the  distant  station,  the 
direction  of  winding  is  sucli  that  the  magnetism  is  suddenly  increaseil  and  the 
armature  is  drawn  to  the  down  pctsition.  It  remains  there  after  the  instan- 
taneous current  has  ceased.  Wlien  tlie  key  at  the  distant  station  is  opened  and 
an  instantaneous  current  in  flie  opjiosite  direction  Hows  through  the  instru- 
ment, the  magnetism  of  the  cores  is  suddenly  decreased  with  the  result  that  the 
armature  flies  to  tlie  up  position  and  there  i-omains.  If  the  line  is  not  too  long 
nor  of  too  high  a  resistance,  and  particularly  il'  llicre  aic  not  too  many  instru- 
ments in  .series  on  the  line,  the  sound  made  by  tills  instrument  Imitates  very 
closely  that  made  by  a  local  sounder.  It  may  be  that  the  imi)uls»'s  from  the 
distant   station   will   come  in   reversed,    and    for  tiiis   purpose   the   double-pole 


(64) 


Telegraphy  and  the  Induction  Telegraph  Set. — Chapter  2. 


33 


double-throw  switch  is  provided  whicli  reverses  llie  connection  of  tlie  sounder  to 
the  line.  If  the  sij,'nals  come  in  reversed,  it  is  only  noccssary  to  turn  tlic  switch 
over  when  they  will  come  in  in  (he  proper  direction. 

Thiorij. 

Figure  2-28  shows  the  theory  of  operation  of  the  held  inductidii  .set.  (Cir- 
cuit .1  comprises  a  key,  primary  of  an  induction  coil,  and  battery.  Circuit  li 
comprises  the  secondary  of  the  induction  coil  and  a  polarized  sounder  or  relay. 
When  the  key  is  closed  in  circuit  ^l  there  is  an  instantaneous  electromotive 
force  inducetl  in  the  secondary  of  the  induction  coil  which  causes  an  in- 
stantaneous current  to  flow  through  the  polarized  Instrument  and  to  bring 
its  armature  to  a  certain  position  in  which  it  will  remain  after  the  in- 
stantaneous current  has  ceased.  When  the  key  in  circuit  ,1  is  opened  there 
will  be  a  similar  instantaneous  electromotive  force  tending  to  make  a  current 
flow  in  the  opposite  direction  in  circuit  B.  This  current  will  bring  the  arma- 
ture of  the  polarized  instrument  to  its  other  position,  in  which  it  will  remain 
after  the  current  has  ceased.  As  this  secondary  electromotive  force  may  be 
very  high,  and  as  polarized  instruments  can  be  made  to  operate  on  extremely 
small  currents,  this  induction  telegraph  arrangement  will  operate  over  lines 
of  high  resistance,  although  the  battery  in  the  primai'y  circuit  may  be  one 
of  only  a  few  volts. 

INSTKUCTIONS    FOR   OPERATING. 


To  mstdll  hatteries. — Open  door  of  the  battery  case  by  releasing  spring  and 
at  the  same  time,  placing  the  forefinger  against  the  inside  of  the  door  through 
the  small  aperture  in  metal  case.  Insert  top  battery  unit,  negative  or  flat  end, 
first  and  lower  unit,  positive  or  bottom  end,  first. 


Fig.  2-29.— TELEGRAPH     INDUCTION    SET,   CIRCUITS. 

To  use  as  an  induction  tclcgraijh  set. — Coiuiect  line  to  binding  posts  1  and  2. 
Lock  circuit  closing  lever  in  the  open  position  by  unscrewing  small  setscrew 
in  key  base  until  it  projects  sutRciently  to  lock  the  lever.  If  the  sounder 
fails  to  respond,  change  the  direction  of  the  current  through  the  sounder  by 
throwing  the  reversing  switch. 

To  vse  as  a  closed-circuit  telegraph  set. — Remove  batteries  from  case.  Con- 
nect line  to  posts  Nos.  2  and  3;  release  circuit-closing  lever  by  screwing  locking 
screw  down  until  it  is  flush  with  the  base. 

(65) 


34  Signal  Corps  Manual  No.  3. — Chapter  2. 

Circnits. — As  an  induction  telegrapli ;  wlien  the  key  is  depressed  current 
from  +  of  l)attery  tlows  through  primary  of  coil,  key,  front  contact  to  —  of 
battery.  The  instantaneous  secondary  current  flows  from  secondary  of  coil, 
through  switch,  polarized  sounder  (operating  it),  to  binding  post  2,  line,  distant 
station,  ground,  binding  post  1,  secondary.  The  instantaneous  secondary  cur- 
rent on  opening  the  key  follows  the  same  path  in  the  opposite  direction.  In- 
coming impulses  through  line  to  binding  post  2  go  through  the  switch,  polarized 
sounder,  key,  back  contact  of  key,  binding  post  1,  ground.  The  purpose  of 
the  back  contact  of  the  key  is  to  short-circuit  the  secondary  of  the  induction 
coil  and  so  remove  its  impedance  from  the  circuit  when  receiving.  It  is  not 
essential  and  the  key  may  be  replaced  by  one  having  no  back  contact. 

As  a  closed-circuit  telegraph ;  external  battery  one  pole  to  ground,  the  other 
to  binding  post  3.  Batteries  in  instrument  removed.  Circuit,  binding  post  3, 
front  contact  of  key,  key,  reversing  switch,  sounder,  binding  post  2,  line.  Note 
that  circuit  closing  lever  on  key  must  be  closed  when  not  sending. 

The  resistance  of  the  primary  of  the  induction  coil  installed  at  present  in 
these  instruments  is  very  low,  and  the  batteries  run  down  very  quickly  in 
service.  All  officers  in  charge  of  installations  using  these  instruments  should 
keep  this  in  mind  and  keep  constant  requisitions  for  new  batteries  going  for- 
ward. Wherever  possible,  as  in  permanent  or  semipermanent  stations,  external 
battery  should  be  installed.  The  type  of  external  battery  is  innnaterial,  about 
G  to  K)  volts  lieing  a  good  E.  M.  F.  to  use. 

DUPLEX    OPERATION. 

The  field  induction  telegraph  set  may  easily  be  duplexed,  following  the  simple 
principles  of  the  differential  polar  duplex  system.  The  only  additional  ecpii])- 
ment  recpiired  is  an  artificial  line  which  can  1h>  adjusted  to  have  the  same 
resistance  and,  with  long  lines,  the  same  capacity  as  the  line  itself.  For  duph'x 
opei-atlon  the  line  nnist  be  connected  to  binding  post  No.  2.  The  green  wire  nor- 
mally connected  to  outside  binding  post  U  on  the  polarized  sounder  nuist  be 
shifted  to  inside  binding  post  U,  and  the  connecting  bar  joining  inside  ?'  to 
inside  1)  must  be  in  place.  The  artifical  line  goes  between  outside  U  and  bind- 
ing i)ost  No.  1,  and  the  ground  is  attached  to  binding  post  No.  1. 

Arli/lcial  line  ior  duplr.r.-^Auy  resistance  box,  sliding  rheostat,  or  other 
variable  resistance  whose  maximum  value  is  equal  to  or  greater  than  the 
resistance  of  the  line  and  distant  instnnnent.  If  th(>  line  lias  appreciable 
capacity,  as  in  the  case  of  a  long  line  or  one  in  cable  or  laid  on  the  gi'ound.  a 
balancing  capacity  can  be  constriictcd  ol'  the  2  m.  f.  condensei's  used  in  common 
battery  tele[>liones.  '^I'liey  are  cheaj)  and  easily  obtained.  Fractions  of  2  m.  f. 
can  be  obtained  by  jiutting  c<tndensers  in  series,  (^lose  static  balance  is  rarely 
necessary. 

Instdlhition. — In  large  offices  the  operators  should  have  in  front  of  them  only 
the  local  sounder  and  key.  All  other  apparatus  should  be  in  a  separate  room 
under  charge  of  an  expert.  This  plan  is  especially  necessary  where  duplex  and 
repeater  sets  are  installed.  In  small  ofiici's  the  circuits  should  be  well  installed 
without  unnecessary  complication,  and  full  instructions  for  operating  and  adjust- 
ing should  be  furnished.  Operators  put  in  charge  of  such  stations  should  receive 
sftecial  instruction  before  assuming  charge,  as  the  induction  telegraph  system  is 
not  used  commercially  at  present,  in  spite  of  its  many  advantages. 


(66) 


ClIAPTKU    8. 
TELEPHONY— THE   CAMP   TELEPHONE   AND   THE   BUZZER. 

Magnktism. 

A  bar  of  steel  or  iron  which  has  the  properties  of  attraftinj^  otlier  pieces  of 
steel  or  iron  is  called  a  nuif^net.  When  freely  suspended  at  its  center  it  will 
point  north  and  south.  It  can  also  impart  these  powers  to  another  piece  of 
iron  or  steel  without  losing  any  of  its  own. 

The  ends  of  a  nfagnet  are  called  its  poles.  The  end  which  jxiints  toward  the 
north  is  its  north  pole  and  the  other  end  its  south  iKile.  The  north  end  of  any 
magnet  will  repel  the  north  ends  of  all  other  magnets,  but  will  attract  all  .south 
poles.  From  this  follows  tlie  law  of  magnetic  attraction  '*  like  poles  repel  and 
unlike  poles  attract." 

The  force  exerted  by  one  magnet  on  another  to  attract  or  repel  it  is  called 
magnetic  force.  If  iron  filings  be  spread  on  a  paper  laid  over  a  bar  magnet,  the 
filings  will  arrange  themselves  about  the  magnet  in  curves  which  end  at  tlie 
poles.  These  curves  are  called  lines  of  force,  and  the  whole  space  occupied  by 
the  curves  is  the  magnetic  field  of  force,  or  magnetic  field.  It  is  assumed  that 
the  lines  of  force  come  out  from  the  north  pole  of  the  magnet,  pass  through  the 
air,  reenter  the  magnet  at  the  south  pole  and  pass  through  it  to  the  north 
pole,  thus  completing  the  ]»ath.  This  path  forms  the  magnetic  circuit,  and  each 
of  the  lines  of  force  completes  it  without  crossing  or  combining  with  any  one 
of  the  others  in  the  field.  A  line  of  force  always  forms  a  closed  h»op  so  that  as 
many  lines  enter  the  south  pole  as  leave  the  north. 

To  make  a  magnet  of  a  steel  bar,  place  the  bar  flat  on  a  table.  Take  the 
south  pole  of  a  magnet  and  stroke  the  bar  with  it  several  times,  always  from 
end  to  end  in  the  same  direction.  The  end  of  the  bar  first  touched  will  then 
become  a  south  pole  and  the  end  where  magnet  last  touched  a  n()rth  pole.  The 
l)ar  will  then  be  a  magnet.  Or  wind  a  few  tin-iis  of  insulated  wire  around  the 
bar  and  pass  a  current  of  electricity  through  the  wire  for  a  slKtrt  time,  gently 
tapping  the  bar  with  a  hannner  while  the  current  is  flowing.  Upon  removing 
the  bar  from  the  coil  it  will  be  found  to  be  a  magnet. 

If  a  piece  of  iron,  mounted  on  a  pivot  so  it  is  free  to  swing  about,  be  phueil 
in  a  magnetic  field  of  force,  the  iron  will  move  so  that  the  greatest  number  of 
lines  of  force  of  the  field  will  pass  through  it.  If  the  movable  body  be  a  magnet, 
for  example,  a  compass,  it  will  turn,  under  the  intluence  of  the  field,  so  that 
not  oifly  the  greatest  number  of  lines  of  force  will  pass  through  it.  but  also  so 
that  its  own  lines  of  force  will  be  in  the  same  direction  as  those  of  the  field. 
Upon  this  fact  is  based  the  construction  of  many  forms  of  electrical  instruments. 

If  a  bar  of  soft  iron  be  placed  in  the  field  of  a  bar  magnet,  we  will  find  on 
testing  the  soft  iron  bar  that  it,  too,  has  become  a  magnet  having  two  distinct 
poles.  The  iron  bar  is  called  the  body  under  induction,  the  magnet  the  inducing 
body,  and  this  phenomenon  magnetic  induction.  Magnetic  induction  is  define<l 
as  the  action  and  reaction  which  occur  when  a  magnetic  field  makes  a  magnet 
of  a  body  placed  therein. 

(67)  1 


2  Signal  Corps  Manual  No.  3. — Chapter  3. 

ELECTROMAGNETISil. 

Every  wire  throiigli  which  a  current  Hows  possesses  a  magnetic  tiehl  arouiul 
it.  This  fact  can  be  proved  by  bringing  a  compass  near  it.  The  magnetic  field 
will  act  on  the  compass,  and  the  needle  will  be  deflected,  showing  not  only  the 
presence  of  a  magnetic  field  but  also  the  direction  of  the  lines  of  force.  The.se 
will  be  found  to  encircle  the  wire,  always  running  from  left  to  right,  similar  to 
the  direction  in  which  the  hands  of  a  clock  move,  assuming  that  the  current  is 
flowing  directly  away  from  the  observer. 

A  solenoid  consists  of  one  or  more  layers  of  wire  wound  on  a  spool,  usually 
of  nonmagnetic  material,  the  length  being  great  as  compared  with  the  diameter. 
A  magnet  can  be  made  of  a  solenoid  by  passing  a  current  of  electricity  through 
the  wire.  One  end  of  the  coil  will  be  the  north  pole  and  the  other  the  south 
pole.  If  an  iron  bar  be  placed  lengthwise  through  the  coil  while  the  current  is 
flowing,  it  will  be  found  that  the  magnetism  has  been  increased.  This  is  due 
to  the  fact  that  lines  of  force  are  much  more  easily  set  up  in  iron  or  steel  than 
in  a  nonmagnetic  medium.  A  solenoid  with  such  an  iron  core  constitutes  an 
electromagnet.  The  current's  magnetic  field  induces  magnetism  in  a  piece  of 
iron  placed  within  its  limits. 

If  the  iron  core  of  a  solenoid  is  pulled  out  while  the  current  is  flowing  the 
attractive  forjce  of  the  solenoid  will  tend  to  pull  the  core  back  until  its  middle 
point  coincides  with  that  of  the  solenoid.  This  principle  is  made  use  of  in 
many  electrical  devices,  such  as  circuit  breakers,  ammeters,  and  telautographs. 
Electromagnets  are  used  in  many  kinds  of  instruments — electric  bells,  tele- 
graph sounders,  telephone  receivers,  and  relays  are  some  examples.  The 
strength  of  any  electromagnet  depends  on  the  number  of  turns  of  wire  and 
the  strength  of  current  passing  through  it. 

Electromagnetic  Induction. 

If  a  straight  wire  be  moved  across  a  magnetic  field  so  as  to  cut  lines  of 
force,  a  difference  of  potential  will  be  set  up  between  its  ends.  If  the  ends 
of  the  wire  be  connected  outside  the  field,  a  current  will  flow.  This  is  called 
electromagnetic  induction,  and  the  currents  so  produced  are  induced  currents. 
Upon  the  principle  of  magnetic  induction  is  based  the  operation  of  all  <lyuamos, 
transform«>rs,  induction  coils,  telephones,  etc. 

No  distinction  is  made  between  tiie  magnetic  field  of  a  ]iermanent  steel 
magnet  and  that  of  an  electromagnet.  P^ithor  the  magnetic  field  or  the  closed 
circuit  may  be  moved  so  long  as  the  lines  of  magnetic  force  are  made  to  cut 
the  wire  of  the  closed  circuit.  Usually  a  coil  of  wire  with  an  iron  core  (electro- 
magnet) is  used  to  produce  the  induction.  It  is  called  then  the  primary  coil, 
or  simply  "primary."  The  clo.sed  circuit,  or  llie  circuit  under  induction,  is 
then  called  the  secondary  coil,  or  "  secondary." 

Clurrent  may  ])e  induced  in  the  secondary  l)y  any  of  the  following  methods: 

1.  By  moving  either  the  i)riiMary  or  secondary  while  current  is  flowing  in 
the  primary. 

2.  Ky  making  or  breaking  the  primary  circuit. 

3.  By  altering  the  current  in  the  jirininry. 

4.  By  reversing  the  dirccdon  of  cuiM-cnl  in  the  primary. 

;".  By  moving  the  iron  core  wliilc  current  Hows  in  the  primarj\ 


(08) 


Telephony — Camp  Telephone  and  Buzzer. — Chapter  3.  3 

El.ECTKOSTATIC     INDUCTION. 

It  liiis  Ih'cii  fduiid  that  an  iiisiilatcMl  ciimliK-ioi;,  siwii  as  a  sheet  of  tin,  an 
aerial-line  wire,  or  a  cable  Cduductor,  has  the  property  of  receiving  an  elec- 
trostatic charge  when  subjected  to  an  electromotive  force.  If,  for  instance,  a 
conductor  of  the  type  mentioned  above  be  thoroughly  insulated  antl  one  ter- 
minal connected  to  one  side  of  a  battery,  the  other  side  of  which  is  grounded, 
p.  certain  amount  of  electricity  will  flow  into  the  conductor  and  appear  upon 
its  surface  as  an  electrostatic  charge,  and  the  potential  of  the  conductor  will  l)e 
raised  to  that  of  the  battery.  The  conductor  in  this  condition  is  said  to  be 
charged  and  holds  an  amount  of  electricity  depending  upon  its  capacity.  The 
charge  is  of  the  same  polarity  as  the  terminal  of  the  battery  to  wliich  the 
conductor  is  connected. 

Experiment  has  determined  that  a  cliarge  ran  not  exist  on  a  conductor 
except  there  be  an  equal  and  opposite  charge  induced  upon  the  bodies  sur- 
rounding it,  and  this  second  induced  charge  is  always  of  opposite  polarity  to 
that  of  the  first  charge.  If  now  the  conductor  be  connected  to  the  ground  it 
will  lose  its  charge,  but  the  charge  of  opposite  sign  on  the  surrounding  bodies 
will  still  be  held,  although  having  no  connection  with  the  first  body  or  with 
the  source  of  electromotive  force.  This  action  by  which  bodies  are  charged 
through  an  insulating  medium  constitutes  electrostratic  induction,  and  the 
arrangement  of  two  insulated  conductors  separated  by  an  insulated  medium 
constitutes  a  condenser.  The  most  common  type  of  condenser  is  the  Leyden 
jar,  in  which  the  insulated  conductors  are  sheets  of  tin  foil,  one  placed  on  the 
outside,  the  second  on  the  inside  of  the  glass  jar,  the  latter  forming  the  in- 
sultating  medium  or  dielectric,  as  it  is  commonly  called.  The  capacity  of  the 
condenser,  or  its  ability  to  receive  an  electric  charge,  varies  In  direct  propor- 
tion to  the  area  of  its  plates  inversely  as  the  square  of  the  distance  between 
the  plates  and  directly  as  the  specific  inductive  capacity  of  the  dielectric. 
Where  air  is  iised  as  the  dielectric,  this  latter  quantity  is  unity.  The  sub- 
stances, other  than  air,  ordinarily  used  as  dielectrics  have  a  specific  inductive 
capacity  of  two  to  three  times  as  great  as  that  of  air.  Condensers  used  for 
telephone  purposes  where  it  is  necessary  to  obtain  considerable  capacity  in 
very  limited  space  are  commonly  built  up  of  alternate  layers  of  tin  foil  and 
paraffined  paper  tightly  pressed,  so  as  to  bring  the  layers  of  tin  foil  which 
comprise  the  plates  as  close  together  as  possible.  The  condenser  is  very 
extensively  used  in  telegraph  and  telephone  work  as  a  means  of  allowing 
alternating  or  pulsating  currents  to  pass  while  preventing  the  flow  of  direct 
currents.  This  is  the  direct  opposite  of  the  functions  of  an  impedance  coil, 
which  imposes  a  very  high  resistance  to  varialtle  currents  while  olTering  little 
resistance  to  the  flow  of  direct  current. 

Principle  of  the  Tuansformer. 

An  induction  coil,  or  transformor,  consists  of  two  independent  coils  wound 
on  the  same  iron  core  and  insulated  from  each  other  and  from  the  core.  Alter- 
nating or  interrupted  currents  in  one  of  the  coils  (called  the  primary)  produce 
a  variable  number  of  lines  of  magnetic  force  in  the  inm  core,  and  thus  currents 
are  induced  in  the  other  coil  (secondary),  so  that  any  E.  M.  F.  that  may  be 
applied  to  the  primary  may  be  changed  to  a  higher  or  lower  one  in  the  second- 
ary. The  ratio  of  primary  to  secondary  E.  ^I.  F.  is  equal  to  the  ratio  of  the 
turns  in  the  two  coils.  For  example,  if  there  are  10  turns  in  the  primary  and 
100  turns  in  the  secondary,  the  induced  E.  M.  F.  will  be  10  times  greater  than 
that  used  in  the  primary.     When  a  low  E.  M.  F.  in  the  primary  is  changed  to  a 

(69) 


4  Signal  Corps  Manual  No.  3. — Chapter  3. 

higher  one  in  the  secondary  coil,  tlie  latter  loses  in  current  strength  what  it 
gains  in  pressure.  For  example,  in  the  above  case,  if  tliere  is  1  ampere  current 
at  10  volts  pressure  in  the  primary  and  the  E.  M.  F.  of  the  secondary  is  100 
volts,  only  0.1  of  an  ampere  of  current  would  he  flowing  through  the  latter. 
This  assumes  that  there  are  no  losses  in  the  transformer.  This  principle  is 
made  use  of  to  generate  very  high  electromotive  forces  such  as  are  used  in 
wireless  telegraphy. 

Theory  of  the  Telephone. 

In  the  act  of  speaking  the  vocal  cords  cause  air  vibrations,  which,  falling 
upon  the  drum  of  the  ear,  are  recognized  by  the  auditory  nerves  as  speech.  If, 
instead  of  falling  on  the  eardrum,  these  vibrations  should  fall  upon  a  diaphragm 
wliich  is  capable  of  changing  them  into  electrical  vibrations,  and  there  is  some 
means  of  transmitting  them  along  a  line  and  again  reproducing  at  the  other  end 
into  similar  air  vibrations,  we  have  the  telephone.  In  order  to  understand  the 
action  of  the  telephone  it  is  necessary  to  define  lines  of  force  and  explain  two 
simple  laws  of  magnetic  indviction.  Lines  of  force  are  imaginary  lines  which 
surround  a  magnet  and  indicate  by  their  position  and  number  the  direction  and 
strength  of  its  action.  The  laws  of  magnetic  induction  referred  to  are :  First, 
if  a  number  of  lines  of  force  thread  or  pass  through  a  coil  of  wire  and  this 
number  is  increased  or  diminished,  a  momentary  current  will  flow  in  the  coil ; 
second,  if  a  coil  of  wire  be  wound  around  a  permanent  steel  magnet  and  a 
current  of  electricity  be  sent  through  the  windings,  it  will,  if  in  a  certain  direc- 
tion, increa.se  the  strength  of  the  permanent  magnet,  and  if  in  the  opposite 
<lirecti(tn  will  diminish  its  strength.  To  understand  how  articulate  speech  is 
transmitted  by  means  of  the  telephone,  let  us  take  the  simplest  case  of  two 
telephone  receivers,  A  and  /;.  (•diiiuH'ted  to  tlic  line  as  shown  in  ligurc  .S-1. 


Fig.    3-1.— TELEPHONE    CIRCUIT    SIMPLIFIED,   USING    TWO    TELEPHONE   RECEIVERS. 

The  telephone  receiver  (a  more  detailed  description  of  which  will  appear 
later)  consists  of  a  .soft-iron  (lia]ihragm  ])laced  close  to  a  permanent  magnet. 
Around  the  diaphragm  end  of  this  magnet  is  wound  a  coil  of  fine  insulated 
copper  wire.  Tlie  air  vibrations,  caused  by  the  act  of  si)eaklng,  Tipon  striking 
the  iron  diaphragm  at  .1  cause  it  to  vibrate.  The  vibrations  of  this  dia- 
phragm produce  changes  in  the  number  of  lines  of  force  which  thread  through 
the  windings  of  tlie  coll.  These  changes,  according  to  the  first  law,  produce 
n  current  in  the  winding  wliicli  will  be  of  greater  or  le.ss  strength  and  in 
opposite  directions,  following  the  vibrations  of  the  diai)hragm.  This  varying 
current  proceeds  along  the  line,  and  when  it  arrives  at  B  will  increase  and 
diminish  the  strength  of  IS's  magnet.  The  variation  of  the  strength  of  B's 
magnet  will  jiroduce  a  varying  jtnll  on  IVs  diai)hragm  and  caus«'  it  to  vibrate 
in  a  manner  similar  to  tiic  diaiiluagni  of  ,1.     The  vibration  of  the  <lia])hragm 


(70) 


Telephony — Camp  Telephone  and  Buzzer. — Chapter  3.  5 

at  li  is  recojiiiizt'd  :is  sduiid  couiiii,:.'  fioiii  .1.  'I'lii'  siiiijilc  circuit  shown  in 
figure  3-1  would  iierniit  a  person  to  talk  or  hear,  as  the  case  may  he.  The  first 
modification  of  the  circuit  (fig.  3-2)  is  to  introduce  two  teleiih<ine  receivers 
at  the  point  A  and  two  at  the  i)oint  li,  all  l)eing  in  series,  one  serving  as  the 
transmitting  and  tlie  other  as  the  receiving  instrument  at  each  point. 

For  certain  reasons  this  type  of  receiver  just  described  does  not  make  a 
good  transmitter,  and  in  practice  is  replaced  hy  a  battery  transmitter. 

A  complete  local  battery  teleplione  instrument  consists  of  a  receiver,  local 
battery  transmitter,  induction  coil,  magneto  generator,  call  hell,  and  certain 
switching  devices  whicii  are  contained   in   the  magneto-generator  box. 


Fig.   3-2.— TELEPHONE   CIRCUIT    SIMPLIFIED,    USING    FOUR   TELEPHONE    RECEIVERS. 

A  complete  common  battery   instrument  consists  of  a   receiver,  transmitter, 
induction  coil,  condenser,  call  bell,  and  hook  switch. 

LOCAL    HATTEKY    THAN  SMISSION. 


The  battery  transmitter  depends  for  its  action  on  the  fact  that  a  varying 
pressure  changes  the  resistance  of  carbon.     The  iransmiftcr  cnnsisfs  of  a  inmi- 


Fig.    3-3.— TELEPHONE  CIRCUIT,    LOCAL   BATTERY.    Si'. 

ber  of  carbon  particles  or  granules  in  a  jiropcr  recei)tacle  with  a  means  ol 
varying  tlie  pressure  upon  the  granules  in  circuit  with  a  battery  and  the  coarst-- 
wire  winding  of  an  induction  coil.  .The  induction  coil  consists  of  a  bundle  of 
soft-iron  wires,  surrounded  by  two  windings  of  insulateil  copper  wire,  one  being 

(-1J 


6  Signal  Corps  Manual  No.  3. — Chapter  3. 

of  coarse  wire,  with  few  turns  and  low  resistance,  called  the  "  primary."  and 
the  other  of  fine  wire,  with  a  large  number  of  turns  and  higher  resistance, 
called  the  "  secondary."  The  relative  position  of  these  various  parts  of  a  local 
battery  instrument  is  indicated  in  figure  3-3,  in  which  T  is  the  transmitter  that 
contains  the  carbon  granules  through  which  the  current  from  battery  B  flows. 
T  also  contains  a  diaphragm  which  presses  on  the  carbon  granules,  or  is  so 
connected  with  them  as  to  vary  the  pressure  between  the  particles  as  the  sound 
waves  fall  on  it.  P  is  the  coarse  and  S  the  fine  wire  winding  of  the  induction 
coil,  which  is  connected  to  the  receiver  R  and  the  line.  The  local  battery 
circuit  includes  B,  P,  H,  and  T.  As  the  air  vibrations  fall  on  the  diaphragm  at 
T  they  produce  a  change  in  the  resistance  between  the  carbon  particles  in  contact 
with  it.  This  change  of  resistance  causes  the  current  flowing  in  the  coarse-wire 
coil  to  fluctuate,  thereby  inducing  an  alternating  current  in  the  fine-wire  coil, 
which  goes  to  the  line  and  receiver  and  reproduces  speech,  as  has  been  explained 
before. 

COMMON  BATTERY  TRANSMISSION. 

The  common  l)attery  telephone  operates  similarly  to  the  local  battery  tele- 
phone in  its  essential  details.  The  principal  point  of  difference  lies  in  the  fact 
that  in  conniion  battery  operation  the  current  which  flows  through  the  transmit- 
ter is  furnished  by  battery  installed  at  the  central  exchange  in  place  of  local 
battery  installed  in  the  instrument,  as  in  the  case  of  the  local  battery  tele- 
phone. In  the  connuon  battery  telephone,  battery  is  supplied  over  the  same 
wires  that  are  used  for  transmitting  speech.  Figure  3^  shows  most  of  the  es- 
sential parts  of  the  common  battery  instrument.  The  induction  coil  for  this 
type  of  instrument  is  usually  provided  with  primary  and  secondary  windings 
having  more  nearly  the  same  number  of  turns  and  resistance  than  is  found  in 
the  local  battei-y  instrument.  The  receiver  and  transmitter  are  practically 
identical  with  similar  parts  of  the  local  battery  telephone.  The  operation  of  a 
typical  set  is  as  follows   (referring  to  fig.  3-4)  : 


Fig.  3-4.— TELEPHONE    CIRCUITS,   COMMON     BATTERY,    SIMPLIFIED. 

Direct  curicni  lioiii  the  positive  side  ol'  (lie  battery  al  liic  ccnlral  (>xchange 
enters  tlie  iiistruincnt  over  the  line  l^\  jiasscs  through  the  hook  //,  primary 
winding  7'  of  liic  induction  coil,  transmitter  7',  and  leaves  the  instrument  by  the 
line  //.  If  now  the  transmitter  T  is  .sjMdien  int<»,  the  diaphragm,  vibrating,  pro- 
duces a  change  in  the  resistance  between  the  carbon  particles  i)laced  near  it 

(72) 


Telephony — Camp  Telephone  and  Buzzer.     Chapter  3.  7 

This  varying  resistance  causes  a  corrospondiuK  variail(»ii  in  the  current  tlowing, 
which  is  received  at  tlie  distant  station  as  speecii.  Tliis  varying  current  in 
the  winding  P  acting  upon  the  winding  .S",  whi<-h  is  placed  upon  tlie  same  core, 
induces  a  curnMit  in  tlie  receiver  circuit  conijiosed  of  the  receiver  R  and  tiie 
winding  S.  In  the  case  of  receiving  from  a  distant  station  the  voice  current  may 
be  considered  to  follow  the  same  course  as  that  taken  l)y  the  battery  current. 
This  current,  however,  is  varial»le,  and  in  passing  tiiniu;,di  the  winding  /'  of  tlie 
induction  coll  Induces  a  current  in  the  receiver  circuit. 

In  tlie  normal  condition  of  tlie  instrument  when  not  in  use  the  receiver  R 
draws  down  the  hook  //,  opening  the  contact,  thus  preventing  the  flow  of  battery 
when  the  instrument  is  not  in  use. 

Owing  to  the  fact  that  the  comni<m  battery  instrument  depends  for  its  opera- 
tion on  direct  current  in  the  line,  the  range  of  such  operation  is  necessarily  lim- 
ited by  the  resistance  of  the  line  circuit.  When  the  resistance  of  the  line  be- 
comes so  high  as  to  materially  cut  down  the  strength  of  current,  loutlness  of 
voice  waves  transmitted  is  correspondingly  decreased. 


The  magneto  generator  is  largely  u.sed  for  producing  the  calling  current.  It  is 
the  simplest  form  of  electric  dynamo  and  consists  of  an  armature  wound  with 
many  turns  of  fine  wire  so  moiuited  as  to  enable  it  to  be  rapidly  revolved  be- 
tween the  poles  of  a  permanent  horseshoe  magnet.  Its  theory  dei»ends  upon  the 
principle  that  if  the  number  of  lines  of  force  passing  through  a  closed  coil  be 
varied  a  dilTerence  of  potential  will  be  developed  between  the  termijials  of  this 
coil,  and  if  an  external  circuit  be  connected  electric  current  will  flow,  the 
direction  of  which  will  depend  upon  the  relative  direction  of  the  lines  of  force 
and  the  movement  of  the  coil. 

The  following  from  "  Telephonology,"  by  Van  Deventer,  clearly  explains  the 
action  of  the  magneto  generator : 

A  magneto  generator  is  shown  in  theory  in  figure  S-H.  N.  S.  represents 
ends  of  the  permanent  magnets.  The  center  opening  is  known  as  the  "  field." 
In  this  is  placed  the  revolving  armaturo  upon  whicli  is  wound  many  turns  of 
insulated  wire.  The  manner  in  which  the  current  is  generated  will  be  under- 
stood from  a  careful  study  of  the  figures. 


C  D 

Fig.  3-5.— TELEPHONE    MAGNETO    GENERATOR.   THEORY. 


Magnetic  lines  of  force  are  flowing  aci-oss  the  field  from  the  .V  to  the  .^  pole. 
To  generrte  a  current  the  wire  must  move  across  the  lines  of  force,  and  in  .1 
the  maximum  nunil)er  of  lines  are  passing  through  the  coil.  The  number  of 
lines  do  not  change  until  the  armature  has  passed  beyond  the  position  shown  in 

(73) 


8 


Signal  Corps  Manual  No.  3. — Chapter  3. 


B  ami  the  voltage  is  0.  A  little  beyond  B  the  lines  begin  to  decrease,  and  cur- 
rent is  generated  until  C  is  reached,  when  the  remaining  lines  are  shortened  out 
of  the  coil  and  the  rate  of  change  ^f  the  lines  is  greatest  and  tlie  voltage  is  at  a 
maxinuun.     This  is  the  peak  or  highest  point  of  the  wave,  shown  in  tigiu'e  3-6. 

AMien  the  position  shown  in  D  is  reached  the  lines  of  force  pass  through  the 
coil  in  the  opposite  direction  and  the  voltage  drops  to  0.  This  continues  as  long 
as  the  crank  is  turned. 

While  the  wire  is  passing  from  the  position  of  .1  to  that  in  B  a  plus  current, 
or,  as  it  is  termed,  a  positive  current,  is  generated  if  the  north  pole  of  the  magnet 
is  on  that  side,  while  from  that  in  C  to  D  a  minus  or  negative  current  is  gen- 
erated, because  the  wire  is  there  subject  to  the  influence  of  the  south  pole. 


Fig.  3-6.— TELEPHONE     MAGNETO,   VOLTAGE    CURVE. 

Plus  current  is  reprcseuted  l).v  Ihe  sign  +  and  minus  currents  by  the  sign  — . 
Current  flowing  flrst  in  ono  dinM-tion  and  tlien  in  anotlier  is  called  jdteniating 
current,  and  flgure  3-G  illustrates  waves  of  a  current  of  this  kind  given  f)y  a 
magneto  generator.  On  the  left  are  flguros  rei)rc.'-!enting  the  voltage,  whil(>  the 
points  0,  1^  2,  etc.,  along  the  curved  lines  represent  the  ditferent  positions 
of  the  wire  iluring  one  I'evolution  and  coi-respond  to  those  in  flgure  3-.").  Start- 
ing at  line  0  where  there  is  no  current,  we  will  suppose  that  the  upper 
curved  line  represents  plus  current  and  the  lower  curved  line  minus  current. 
From  this  it  will  be  seen  that  current  from  the  telephone  generator  Hows  first 
in  one  direction  and  then  the  otliei-,  the  voltage  increasing  from  0  to  1,  and 
then  decreasing  to  2,  as  the  wire  .-it  this  iM)int  (see  /?,  fig.  3-5)  is  no  longer 
cutting  across  the  lines  of  force,  'i'lie  current  then  increases  to  3  in  the  opposite 
direction  (.see  C,  fig.  3-;")),  and  again  di'creases  to  0  (/>,  fig.  3-5). 

Magneto  generators  u.sed  by  (he  Signal  Corps  are  provided  with  an  automatic 
device  which  opens  the  ai'uiature  circuit  when  the  armature  is  at  rest. 

At  tlie  usual  rate  of  turning  the  magneto  generator  by  hand  tlu>  voltage  will 
be  about  65  to  75  and  the  frequency  about  15  complete  cycles,  or  30  alterna- 
tions, per  second. 

In  figure  3-7,  A  shows  the  generator  armature  on  which  are  wound  the  many 
turns  of  fine  wire  wliich  are  revolved  in  the  magnetic  field  referred  toabov(>. 
It  will  be  noted  that  this  armature  is  made  of  a  large  number  of  thin  stamped 
metal  pieces  which  are  as.sembled  on  the  arniiiture  shaft  as  shown.  In  i)art  /{ 
of  the  above  figure  the  generator  armature,  wound,  has  been  placed  within  the 
generator  frame.  Contact  jiieces  of  the  device  for  closing  the  generator  circuit, 
mounted  in  place  on  end  of  the  generator  frame,  are  shown  in  the  figure.  On 
the  other  end  a  gear  wliich  meshes  with  a  small  piinon  on  armature  shaft  and 
a  crank  for  revolving  arc  shown.  \\'hcn  crank  is  roinled  in  clockwise  direction, 
tlie  shaft,  upon  which  is  mounted  the  gi'ar.  automatically  protrudes  througli 
end  of  frame,  thereby  closing  the  two  contact  i)ieces  which  automatically  ojuMi 
when  revolving  of  crank  cejises. 

C  shows  a  conii)lete  generator  of  Ihe  5-h,ii-  type,  with  horseshoe  ni;ignets  in 
place. 

(leneriitoi's  nse(|  by  the  Signnl  Corps  ;ii-e  provided  with  3,  4,  or  5  bars,  depend- 
ing upon  the  class  of  .service  in  whidi  they  ;ii-e  |o  be  used. 

(74) 


Telephony — Camp  Telephone  and  Buzzer. — Chapter  3. 


fig.  3-7.— telephone,  magneto  generator. 

Receiver. 

A  linnd  ree-oiver  of  the  t.vi)o  now  usoil  in  tlii'  Sii^nal  I'oi'ii.s  is  .shown  in  tijrure  3-S. 
It  consists  of  a  U-shaped  permanent  magnet  t,  to  the  ends  of  whieli  are  fastened 
soft-iron  jioie  pieces  p  p.  Over  each  pole  piece  i.s  a  coil  of  Hne  wire  wound  on 
a  l)ohhin  witli  nonmagnetic  metal  heads.  These  coils  are  connected  in  series 
in  such  a  manner  as  to  make  the  front  end  of  one  the  north  pole  and  the 
similar  end  of  the  other  the  south  pole  when  current  flows  through  both  coils  in 
a  certain  direction.  The  combined  resistance  of  the.se  coils  connectetl  in  series  is 
about  SO  ohms.  The  pole  pieces  pass  through  the  bottom  of  a  metal  cup  C. 
which  is  thus  secured  firmly  in  place.  The  diaphragm  <!,  of  soft  iron,  tinned  or 
enameled,  rests  on  the  rim  of  this  cup.  A  clamping  ring  /  screws  onto 
the  metal  cup  C.  thus  holding  the  diaphragm  d  firmly  in  place.  The  receiver 
cords  are  connected  to  terminals  »;,  a  strain  cord  lieing  attached  to  the  1<m»j)  of 
tlu'  magnet  to  provide  against  injurx-  to  the  cord  conductors.    As  tiius  a.s.si-ml)le<| 


46581°— 17- 


-6 


(75) 


10 


Signal  Corps  Manual  No.  3. — Chapter  3. 


tlie  receiver  is  operative  and  may  l)e  so  nsed  in  ease  of  accident  to  the  contain- 
ing shell  and  cap.  This  shell  iS  slips  o\er  the  working  parts  of  the  receiver  and 
is  held  in  place  by  the  earpiece  g,  which  screws  onto  the  shell.  The  separation 
of  the  diaphragm  from  the  pole  piece  varies  with  the  different  types  of  receivers, 
the  usual  separation  being  about  0.014  inch. 

The  operation  of  the  receiver  is  as  follows : 

The  pole  pieces  p  p,  being  attachetl  to  the  ends  of  the  permanent  magnet  t, 
have  one  a  north  and  the  other  a  south  polarity  and  the  magnetic  circuit  is 
completed  from  one  pole  to  the  other  through  the  soft  iron  diaphragm  d, 
which  is,  therefore,  drawn  toward  the  poles  and  held  in  constant  tension. 
If  now  a  current  flows  through  the  coils  in  such  a  direction  that  the  lines 
of  force  due  to  it  coincide  with  those  of  the  permanent  magnet,  the  diaphragm 
will  be  pulled  closer  to  the  pole  pieces,  due  to  the  increased  strength  of  the 
magnetic  field.  If  the  current  flows  in  the  opposite  direction,  the  strength 
of  the  magnetic  fleld,  due  to  the  permanent  magnet,  will  be  reduced  and  the 
diaphragm  will  spring  farther  from  the  poles.  It  will  thus  be  seen  that 
wliether  tlie  lines  of  force  due  to  the  current   in   the  coils  assist  or  oppose 


Fig.   3-8.— TELEPHONE    HAND    RECEIVER. 

tliose  due  to  the  perniiinent  magnet,  a  varying  pull  is  produced  on  tlie  dia- 
phragm that  causes  vibrations  in  the  latter  in  unison  with  the  changes  in 
currcMit.  The  movement  of  the  diaphra.gm  will  thus  set  up  vibrations  in 
the  surrounding  air  which  may  be  perceived  as  sound. 

Transmitter. 

The  operation  of  the  transinitlci-  di'pcnds  on  llie  fact  that  the  ehuMrical 
resistanct;  lietween  two  or  more  bodies,  either  in  light  or  loose  contact,  varies 
with  changes  in  the  j)ressure  between  the  bodies.  The  change  in  resistance 
is  du(*  to  variatifin  in  the  area  of  contact  surfncc  between  the  grainiles  and 
electrodes  and  not  to  compression  of  the  caii»on  granules  themselves.  In 
general,  the  transmitters  used  by  the  Signal  Corps  dei)end  on  this  principle. 
A  typical  transmitter  is  shown  in  figure  3-9.  A  metal  cup,  .1,  forms  the  front 
electrode  and  is  attadnMi  to  (lie  diai)hragm  for  sending.  The  rear  electrode 
is  held  rigidly  in  a  metal  bridge  i)iece,  /*',  which  is  in  turn  fastened  to  the 
frame  which  sujijtorts  tlie  mouthpiece  (I,  and  the  remainder  of  the  transmit- 
ter.    This  rear  electrode  consists  of  a  hard,  ]>olished,  carbon  button,  .1/,  secured 


(7G) 


Telephony — Camp  Telephone  and  Buzzer. — Chapter  3. 


11 


to  a  brass  hultim  between  two  parts  <if  wbidi  is  clamped  a  mica  ring  or 
diaphragm,  O,  the  outer  edge  of  whicli  is  clamped  against  the  front  electrode, 
A,  by  means  of  a  metal  ring,  S,  which  screws  over  .1.  The  space  between 
the  front  and  rear  electrodes  is  partly  filled  with  hard  granular  carbon  of 
uniform  size.  Two  dampening  springs,  B  and  C,  are  provided  to  prevent 
vibration  of  the  diaphragm  at  its  natural  period. 


.-G 


Fig.   3-9.— TELEPHONE  TRANSMITTER. 

The  operation  of  the  transmitter  is  as  follows : 

Current  from  a  battery  passes  from  one  terminal,  E,  to  the  carbon  electrode 
through  the  granular  carbon  to  the  metal  cup  which  forms  the  other  electrode. 
If  the  transmitter  now  be  spoken  into,  the  diaphragln  and  cup  vibrate  in 
unison  with  the  sound  waves  produced  in  the  air,  thus  causing  the  pressure 
between  the  front  and  rear  electrodes  on  the  granular  carbon  to  vary  and  thus 
change  the  resistance  of  the  transmitter.  Therefore,  variations  in  the  current 
are  set  up  which  correspond  exactly  with  the  voice  vibrations  which  reach  the 
transmitter  diaphragm. 

Ringer. 

The  magneto  generator  is  commonly  used  in  coimection  with  a  polarized  bell, 
or  ringer,  as  it  is  usually  called,  by  means  of  which  audible  signals  indicate 
the  incoming  calls  on  the  telephone  instruments.  The  usual  form  of  this 
piece  of  apparatus  is  shown  in  ligure  3-10.  In  this  figure  c  c  represents  soft- 
iron  cores  upon  which  are  wound  coils  of  fine  wire  connected  in  series  with 
the  line  wires  I  I'.  N  S  is  a  permanent  magnet,  and  .t  a  .soft-iron  armature 
I)ivoted  at  its  center.  A  slender  rod  terminating  in  a  small  metal  ball  is  at- 
tached to  the  center  of  the  armature.  Wlien  no  current  is  flowing  through  the 
coil  the  permanent  magnet  A'^  S  causes  the  upper  ends  of  the  cores  to  be  north 
poles  and  the  opposite  ends  to  be  south  poles.  In  this  condition  the  armature 
will  be  attracted  by  both  cores  and  will  rest  against  one  or  the  other  as  may 
chance  to  happen.  If  now  current  passes  through  the  coils  in  series  in  such 
direction  as  to  increase  the  strength  of  the  north  pole  /.  and  to  make  r  south 


(77) 


12 


Signal  Corps  Manual  No.  3. — Chapter  3. 


pole  or  weaker  north  pole,  then  /  will  nttract  the  end  of  the  arnmtnre  opposite 
it.  while  c  will  repel  this  end  of  the  armature  or  attract  it  with  smaller  force. 
If  the  current  is  now  reversed  in  direction  so  that  /  becomes  a  south  pole  or  a 
weaker  north  pole  and  e  a  stronger  north  pole,  the  action  will  be  reversed,  c 
will  attract   its  end  of  the  armature  and  /  repel   its  end  or  attract  it  with 


Fig.  3-10.— TELEPHONE   RINGER. 

smaller  force.  With  the  rinser  connected  to  the  magneto  generator  as  shown 
in  this  figure,  the  armature  will  vibrate  between  the  two  gongs  with  the  same 
freciuency  as  the  current  produced  by  the  hand  generator,  and  a  practically 
continuous  ringing  soiind  will  result.  Practically  all  of  the  ringers  used  by 
the  Signal  Corps  are  wound  to  a  resistance  of  1,000  ohms. 

Typks  of  Instruments. 

The  principles  upon  which  depends  the  operation  of  the  various  parts  of  the 
telei)hones  have  been  explained  in  the  preceding  pages.  The  complete  circuits 
of  tlie  instruments  of  the  various  types  ti.sed  by  the  Signal  (^orjvs  will  now  be 
lonsidercd.  and  it  will  be  assumed  that  the  operation  of  the  various  parts  as 
explained  above  is  un<lerstood.  and  will  not  be  discussed  further.  The  instru- 
ments herein  described  have  been  selected  as  being  typical  of  those  now  in  use, 
and  while  .slight  modifications  of  the  circuits  shown  m;iy  be  encountered,  it  is 
Itelieved  that  if  u  person  fiimiliarizes  himself  with  these  circuits  no  trouble 
will  Ite  experienced  in  mastering  any  which  are  slightly  different. 

It  will  be  noted  that  desk  t(>lephones  of  local  battery  and  conmion  battery 
types  employ  precisely  the  same  princii)Ies  as  wall  te!ei>hones,  but  that  it  is 
necessary  to  modify  circuits  iiiid  relative  i)Ositions  of  component  iiarts  in  order 
to  meet  requirements  whereby  the  ringer  (and  magneb*  generator  in  local 
battery  instrmnents)  are  .stationary  and  the  transmitter,  r(>ceiver,  and  book 
switch  (as  u  unit)  are  movable.    To  accomplish  this,  all  manufacturers  employ 


(78) 


Telephony — Camp  Telephone  and  Buzzer.— Chapter  3. 


13 


the  woll-kiiow  II  (U'sk  stand  iiml  riii^icr  Ixtx.  inniicctin^  Ihc  two  liy  means  of  a 
ll('Xil)le  cord  consisting?  oT  two  or  more  conductors.  Some  manufacturers  place 
the  induction  coil  in  tlie  ringer  box  and  otliers  in  tlie  base  of  the  desli  stand. 

Circuits  of  the  local  battery  telephone  are  as  follows,  reference  being  made  to 
figure  3-11. 

licimj  ctillcil. — Hoolc  switcli  contacts  shown  in  diagram  as  closed  would  be 
open,  as  receiver  would  not  be  removed  from  ho<ii<  of  hook  switcli.  Magneto 
g«Mierator  current  enters  at  A.  to  ringer,  to  //. 

CiiUinfi  (Jistdiit  fit(iti(rii., — Hook  switch  contacts  shown  in  diagram  as  closed 
would  be  open,  as  ivceiver  would  not  be  removed  from  hook  of  hook  switch. 
Revolving  crank  of  magneto  generator  contact  at  r  is  closed  and  circuit  is  C  to  A. 
thri>ugh  one  side  of  line,  to  ringer  of  distant  station,  through  other  side  of  line, 
//  to  A. 

It  will  be  noted  that  ringer  of  station  calling  will  also  be  operated.  The 
reader  will  bear  in  mind  that  the  windings  of  ringers  are  of  high  impedance, 
which,  as  previously  explained,  otTers  a  very  high  resistance  to  the  high  fre- 
quency alternating  currents  transmitting  the  sound  wfives,  and  for  this  reason 


Fig.  3-11.— TELEPHONE,    LOCAL    BATTERY,   CIRCUITS. 

they  can  be  connected  direct  across  the  line.  The  magneto  .generators  are 
callable  of  operatin.g  forcibly  under  usual  line  conditions  api)roximately  10 
ringers. 

Li)itcni)ig. — Hook-switch  contacts  are  closed  as  shown  in  diagram  as  receiver 
should  be  removed  from  hook.  A  high  voltage,  high  frequency  alternating  cur- 
rent from  distant  telephone  enters  at  L,  passes  through  receiver,  secondary  of 
induction  coil,  contact  1,  hook  of  hook  switch,  and  L'. 

Tallinff. — Hook  switch  contacts  are  closed,  as  shown  in  diagram,  as  receiver 
would  be  removed  from  hook.  Direct  current  flows  in  primary  circuit  as  fol- 
lows: Battery,  transmitter,  contact  2,  hook  of  hook  switch,  contact  1,  primary 
of  induction  coil.  Voice  waves  fall  on  diajihragm  of  transmitter,  varying 
strength  of  current  in  primary  circuit,  thereby  inducing  in  secondary  of  induc- 
tion coil  a  high  voltage  and  high  frequency  alternating  current  which  is  trans- 
mitted to  distant  receiver  by  means  of  the  following  circuit :  Secondary  of  in- 
duction coil,  contact  1  of  hook  switch,  hook  switch,  L',  one  side  of  line,  circuit 
of  distant  telephone,  other  side  of  line,  L.  receiver,  connection  to  induction  c«)il. 

A  few  commercial  standanl  local  battery  telephones  are  shown  in  ligures  :i-V2 
to  .'i -15,  which  follow  , 


(70) 


14 


Signal  Corps  Manual  No.  3. — Chapter  3. 


^ 

m 

A 

^^rj^M 

1 

rm 

•-€ 

I 

1 

f 

0 

3 

1 

''^^^H 

Fig.  3-12.— TELEPHONE,  WALL,   L.   B.,  SUMTER    MFG.  CO.,   AND    CIRCUITS. 


Backboard 

Shelf  with  hinges 

Transmit  (cr 

TransmittLT  mouthpiece 

Tran.sniittor  bracket 

Transiniilcr-l)rackct  arm 

Ueceiver,  hand 

Receiver,  hand,  cord 

Bindinm)()stline 

I'.iiuiiiij,'  post  for  receiver  cord.. 

li  iiif,'('r, complete 

k  inj.'(T,  KoiiK  for 

Iiin>,'('r,  hammer  and  armature. 

ItiiiKcr.coil  (2  to  a  set) 

Switch,  hook,  complete 

Swilcli,  hook,  liook  fcir 

Switch,  hook,  contact  springs. . 

Coil,  iiuiiiclion 

Mat;ncl(),  complete 

iM;iKiicio, crank  handle 

Mafrnc|(),p('rni;uiot  magliot.  . .. 

Ma>,'ncto,  arnialiire  for 

Magneto,  froiir  for 

Magneto,  pinion  for 

Magneto,  contact  spring  for. . . . 


(80) 


Telephony — Camp  Telephone  and  Buzzer. — Chapter  3.  15 

l.OtAI.    ItATTKKY    WAl.I.    TKI.KrilONK. 

The  circuits  of  tlic  Iticiil  hatlcry  wall  tclcpiioiu'  nC  tin-  Suiiilcr  Ti'lephone 
Maiuifacturiuji;  ('o.'s  iiialce  are  sliuwn  in  tit^urt'  3-12. 

Tliis  tif,'ure  imlicates  the  actual  wirin;;  nl'  tlie  instruineiit  ami  liic  parts  cor- 
rectly, placed  with  relation  to  each  other  as  they  are  niounteil  in  tiie  instru- 
ment.   The  circuits  of  this  instrument  may  he  traced  as  follows: 

1.  Incoming  signals  enter  at  line  //,  pass  to  hinge  C,  to  hell  /{.  to  hinge  f", 
and  return  to  line  L.  The  hook  switch  is  shown  in  its  normal  position  with  the 
hand  receiver  in  place,  all  contacts  heing  open. 

2.  Outgtting  signals  pass  from  one  pole  of  the  generator  (1  to  the  line  /,. 
through  the  distant  instrument  and  return  on  7/  to  hinge  C\  to  the  opposite 
pole  of  the  generator  C.  In  this  instrument  the  hells  li  are  permanently  con- 
nected hetween  the  lines  T.  and  //.  as  is  also  the  generator  (!.  The  latter, 
however,  by  means  of  its  switching  device,  is  open  circuited  when  not  in 
operation. 


-O     Lines    O 


lOOOco 


)ffiK°X° 


3  conductor  cord 


Fig.   3-13.— TELEPHONE.    DESK,    L.    B..    SUMTER    MFG.   CO..  CIRCUITS. 

(81) 


16 


Signal  Corps  Manual  No.  3. — Chapter  3. 


3.  Tlic  IdCiil  li;itt(M-y  aiul  1  i-aiisiiiitlcr  cii-cuits  pass  Iroiii  the  l)alt('i-y  llirou.iili 
the  transiiutt«n'  and  Iht'  cdarse-wire  windinir  of  the  iiiductiun  coil  throusli  the 
hook  switch  //,  wliich  now  has  all  contacts  closed,  to  the  opposite  pole  of  the 
battery.  The  receiving  circuit  passes  from  L'  to  the  liook  switch  H,  through  the 
tine-wire  winding  of  the  ind\iction  coil,  through  the  receiver  R,  to  the  line  L. 

T.OCAL    BATTERY    DESK    SET. 

In  figure  3-13  is  shown  circuits  of  the  local  battery  desk  telephone  of  the 
Sumter  make,  as  furnished  to  the  Signal  Corps.  The  usual  bridging  circuit  is 
used.  The  diagram  shows  the  actual  wiring  as  it  is  found  in  the  instrument, 
and  the  vario\is  parts  are  shown  Ci)rrectly  placed  with  respect  to  each  other. 


Fig.  3-14.— TELEPHONE,   WALL,    L.    B.,   GARFORD     MFG.   CO.,  CI  RCUITS. 

The  wiring  of  llie  (Jarlurd  local  ballery  wall  iclciilicnic  wliicli  is  furiiisjied 
by  the  Signal  ('orps,  is  shown  in  tigure  .'{-14.  In  Ibis  li.gure.  .1  shows  a  sim- 
plified circuit,  and  li  the  wiring  as  actually  found  in  the  instrument  with  tb(> 
parts  correctly  locateil  with  respect    l<i  cadi  otlicr. 

FigUH'  .'V-1.">  shows  the  C.-irford  local  batlcry  desk  telephone  and  the  circuits 
employed  witli  tliLs  in.'<trumcnl. 


(82) 


Telephony — Camp  Telephone  and  Buzzer. — Chapter  3. 


17 


Fig.  3-15.— TELEPHONE,   DESK.   L.  B.,  GARFORD    MFG.  CO. 


Ringer  box,  complete 

Ringer  box,  door  for 

Ringer  box,  screw  fastener  for 

Ringer  box,  binding  post,  line 

Ringer  box,  binding  post,  main  cord 

Ringer,  complete 

Ringer,  gong  for 

Ringer,  hammer  and  armat  ure 

Ringer  coil  (two  to  a  set) ". 

Ringer,  armature  adjusting  screw 

Magneto,  complete  (give  number  of  bars; 

Magneto,  crank  handle 

Magneto,  permanent  magnet 

Magneto,  armature  for 

Magnet  o,  gear  for 

Magneto,  pinion  for 

Magneto,  contact  spring  for 

Coil,  induct  ion 

Desk  stand,  complete  with  transmitter,  receiver,  and  main  cord . 

Desk  stand,  head  for 

Desk  stand,  hook  switch 

Desk  stand,  switch  hook 

Desk  stand,  cord  terminal  block 

Desk  stand,  cord  terminal  block,  binding  post  for 

Transmitter,  complete 

Transmitter,  mouthpiece  for 

Receiver,  hand,  complete 

Receiver,  shell  for 

Receiver,  cap  for 

Cord,  main 


COififOX    UATTKKY    TKl.EPHONK. 


In  general  it  may  be  .'^aiil  that  the  parts  used  in  the  coininon  liattery  wall 
telephones  are  similar  to  those  used  in  the  local  battery. 

It  will  usually  be  found  that  the  priuuiry  »»f  the  induetion  o»ii  use«l  in  the 
common  btitterv  instruments  is  of  lusher  resistance,  and  that  the  ratio  l>etween 


(83) 


18 


Signal  Corps  Manual  No.  3. — Chapter  3. 


tlu>  primary  and  secondary  windiii^is  of  (ho  induction  coils  arc  <iuil(>  dilToront. 
Tlio  distin^iuishinj;  difference  between  the  connnercia!  local  battery  telephone 
and  common  battery  telephone  is  that  the  connnon  battery  instrument  is  not 
equipped  with  a  magneto  generator  for  calling,  or  batteries  for  furnishing 
current  for  transmitting  sound  waves,  and  is  equipped  with  a  condenser  in 
series  with  the  ringer.  The  secondary  of  induction  coil  in  the  local  battery 
telephone  is  in  series  with  outside  line  and  receiver  when  receiver  is  removed 
from  switch  hook,  while  with  the  common  battery  instrument  under  similar 
ci)nditions  the  secondary  of  induction  coil  is  in  series  with  receiver,  transmitter, 
and  condenser,  the  primary  of  induction  coil  being  in  series  with  transmitter 
and  outside  line.  By  reference  to  figure  3-16,  which  shows  circuits  of  the 
common  battery  telephone,  it  will  be  noted  that  the  paths  of  both  the  current 
in  primary  of  induction  coil  and  current  in  secondary  of  induction  coil  traverse 
the  same  line  through  transmitter.  They  do  not  interfere  with  each  other  in 
any  way,  and  the  transmitter,  being  of  low  ohmic  resistance  and  practically 
zero  impedance,  offers  comparatively  no  resistance  to  either. 


LINE    BINDING   POSTS 

-o    o 


Fig.  3-15.— TELEPHONE,    WALL,    C.    B..    WESTERN    ELECTRIC    CO.,    CIRCUITS. 

The  reason  for  this  rearrangement  of  component  parts  is  due  to  tlie  fact 
that  battery  for  furnisliing  necessary  current  for  operation  is  remote  from 
location  of  telephone  and  is  conduclod  to  instrument  l)y  means  of  tlie  line  wires. 
The  battery  lisually  consists  of  12  or  If)  cells  of  stora.ge  battery  having  a  voltage 
of  24  or  IM),  resjiectively. 

While  the  ohmic  resislaiicc  of  tlit^  I'ingcr  is  com])arativ(>ly  high,  usually 
being  l.(MM)  ohms,  it  will  he  svrii  thiil  by  connecting  this  direct  across  the  lint* 
a  considerable  waste  of  curreni  would  ensue,  conseipiently  the  condenser  wliich 
oi»ens  tlie  direct  current  circuit  is  jihiced  in  seiies  with  the  ringer  across  tlie 
line.  An((tlier  reason  for  this  condenser  is  that  with  the  commercial  connnon 
l)attery  telei)hone  the  o))erator  at  switchboard  is  sigiinled  by  merely  removing 
receiver  from  liook,  thereby  closing  the  direct  cm-rent  circuit  through  a  mag- 
netic device  at  switchltoard.     The  <levices  are  ordinarily  of  200  ohms  resist- 


(84) 


Telephony — Camp  Telephone  and  Buzzer. — Chapter  3. 


19 


iuifo  nn«l  opprnio  on  iipiirfixiinaloly  (».oi  of  :iii  jihiiuth  of  ciirnMit,  so  that  Ity 
roferriuf;  to  Oliin'.s  law  in  cliapter  1  tlit?  reader  can  readily  determine  that  this 
.signal  would  he  held  closed  if  the  l,00()-ohin  ringer  were  connected  directly 
across  the  ordinary  line  without  condenser  In  series. 

A  few  commercial  standard  common  batlery  telephones  are  shown  in  figures 
o-lT  to  [i---  which  follow. 


THEORY 


A  B 

Fig.   3-17.— TELEPHONE,    WALL.   C.    B.,    SUMTER    MFG.   CO..  CIRCUITS. 

The  circuits  of  the  common  battery  wall  telephone  of  the  Sumter  Manu- 
facturing Co.  are  shown  in  figure  3-17.  .1  shows  the  wiring  of  the  instrument 
and  the  parts  with  correct  relation  to  each  other,  and  B  a  simplified  circuit 
diagram  of  the  in.strument.     The  operation  of  the  instrument  is  as  follows: 

Assuming  that  the  receiver  is  in  place  on  the  hook  switch,  the  incoming 
ringing  current  will  pa.ss  from  the  line  //  through  the  hells  li,  condenser  C\  to 
the  line  L,  ringing  the  bells  B.  The  hand  receiver  lieing  removinl  from  the 
hook  switch,  the  contacts  at  II  are  closed.  In  this  condition  the  battery  from 
the  central  exchange  passes  from  L'  through  the  coar.se-wire  winding  of  the 
induction  coil,  through  the  transmitter  to  the  line  A,.  Rattery  als«»  pas.ses 
from  the  bells  /?,  secondary  or  fine-wire  winding  of  the  induction  coil,  re<'eiver 
A',  transmitter  T,  to  the  line  /,.     The  resistance  of  this  second  path   is  very 


(85) 


20 


Signal  Corps  Manual  No.  3. — Chapter  3. 


imich  greater  than  lliat  of  tlie  lirst  path,  so  tliat  thi-  current  Mowing  in  this 
liifih  resistance  i)ath  may  l)e  considered  nejilijiible.  If  now  the  transmitter  be 
spolven  into,  the  current  flowing  through  the  transmitter  will  vary  by  reason 
of  the  varying  resistance  of  the  transmitter  caused  by  varying  pressure  between 
the  carbon    granules.     These   fluctuations   in    current    result    in    a    fluctuating 


Fig.  3-18.— TELEPHONE,    DESK,  COMMON   BATTERY. 


Part 
No. 


Reference 

No. 


De.sk  stand,  complete,  with  receiver,  transmitter,  and  cord. 

Bell  box,  complete 

Coil,  induction 

2  m.  f .  conden-ser 

Hook 


Ilookswitch,  complete 

iiecei  ver,  hand 

Receiver,  .shellfor 

Kecfiiver,  earcap  for 

Ue<'pi  ver  diaphragm 

Receiver  diaphruKm,  retaining  ring. 

{'ord,  receiver 

Cord,  main 

Tran.smitter 

Transmitter,  diaphragm  for 

Transmitter,  mouthpiece  for 

Binding  post,  line 


(SC) 


Telephony — Camp  Telephone  and  Buzzer. — Chapter  3. 


21 


■f 

p 

^ 

1 

1 

»* . 

j 

1       V^^^ 

i 

I 

Mwo't'-ly                                       II 

7^ 

^^r 

/  f  v^n 

-F"-'ti\ 

1  <^»^ 

1  ^^ 

SI 

p 

III 

i»«i\J 

V_ 

-^ 

^^^^-    \^ 

Fig.  3-19.— TELEPHONE,   WALL,  COMMON  BATTERY. 


Part 

No. 


Name. 


Bindinf;  post,  line 

Coil,  induction 

Coil,  indviction,  terminals. 

Condenser 

Hook 

Hook,  switch,  complete. . . 
Receiver,  hand 


Refer- 
ence 
No. 


Part 
No. 


Name. 


Receiver,  shell  for 

Receiver,  ean-ap  for 

Receiver  diaphropm _.  - .  - 

Receiver,  diaplirapm.  retaining  ring. 
Rei-eiver,  cord  for,  with  terminals... 
Ringer,  complete 


Refer- 
ence 
No. 


(87) 


22 


Signal  Corps  Manual  No.  3. — Chapter  3. 


current  in  the  primary  of  iutluotiou  t-oil  in  telephone  at  distant  station  and  in- 
duce in  the  secondary  of  same  induction  coil  a  high-voltage,  high-frequency 
alternating  current  which  affects  the  receiver,  thereby  reproducing  speecli.  In- 
coming speech  follows  the  same  circuit  as  that  taken  by  the  battery  from  the 
central  exchange.  This  voice  current,  however,  being  pulsating  in  character, 
induces  a  current  in  the  fine-wire  winding  of  the  induction  coil.  This  current 
passes  through  receiver  R.  hook  switch,  transmitter  T,  and  condenser  C.  thus 
reproducing  in  the  receiver  R  the  sounds  impressed  on  some  distant  transmitter. 
The  condenser  also  serves  to  strengthen  the  effect  of  the  induced  current  in  R 
by  reason  of  the  varying  potential  across  its  terminals. 


B/ue 

Fig.   3-20.— TELEPHONE,    WALL,    C.    B.,    N.    E.   CO.,    CIRCUITS  AS    INSTALLED. 

Figure  ;{-lS  shows  (lie  gonci-al  arraiigcnienl  of  a  conmioii  hallery  desk  tele- 
phone ami  figure  .'{-ID  shows  the  general  arrangement  of  tiie  common  battery 
wall  telepiione.  The  circuits  siiown  or  modilicalions  of  lliem  are  used  by  all 
maiHifacturers  and  the  general  appearance  of  (lie  apparatus  closely  resembles 
that  ."iliown  in  the  illustrations. 


(88) 


Telephony — Camp  Telephone  and  Buzzer. — Chapter  3. 


'J  3 


Figure  3-20  shows  tlic  ciiciiils  as  iiistallt'd  of  a  Noiili  i;it'<iri<-  (Jo.  C.  B.  wall 
teloplione.  Fi;;uiv  ."i-LM  sliows  the  circuits  as  luniisiied  in  the  desk  set  type 
of  the  same  iuslruuieiil. 


Fig.   3-21.— TELEPHONE,    DESK,   C.    B.,    N.    E.   CO..   CIRCUITS   AS    INSTALLED. 

Fifjure  ',i-2'2  shows  the  circuits,  as  installed,  of  a  coininoii  liattery  desk  tele- 
phone, having  the  induction  coil  located  in  the  base  of  the  desk  stand. 


^    ©"fT* 


THEORY 


BEJ_LBOX  DESK  STAND 

Fig  3-22.— TELEPHONE.  DESK.  C.   B..  GARFORD    MFG.  CO. 
CIRCUITS  AS  INSTALLED. 


The  Camp  Telephonk. 

This  teleplione,  wliicli  supers»^h>s  the  field  iclcphiMic.  was  develop*^!  I>y  the 
Signal  Corps  f(»r  use  In  connection  with  camp  leleplione  systems  anil  small  arms 
target  range  systems,  and   may  he  installed   in   tents  ami  structure.s.  or  eon- 

(89) 


24 


Signal  Corps  Manual  No.  3. — Chapter  3. 


sidered  a  portable  iut;triiiiient  for  use  in  llie  Held  for  testing  lines  or  other 
purposes. 

It  is  of  local  battery  type.  The  battery  employed  is  one  unit  of  tungsten 
type  A  described  in  chapter  No.  1.  Figures  3-23  and  3-24  illustrate  this  tele- 
phone, it  being  sliown  dismantled  in  figure  3-24  to  facilitate  identification  of 
parts  in  connection  with  the  preparation  of  reipiisitions  for  renewals. 

The  first  lot  of  these  instruments  M'as  equipped  with  2-bar  magnetos  and 
due  to  its  limitations  the  instrument  could  not  be  used  for  long-distance  work. 
The  new  model  of  this  instrument  will  be  equipped  with  a  3-bar  magneto,  em- 
ploying a  special  high  grade  steel  for  permanent  magnets,  and  while  in  other 
featin-es  there  may  be  a  slight  deviation  from  following  description,  it  is  be- 
lieved that  figures  3-23  and  3-24  can  be  used  in  preparing  requisitions,  it  being 
merely  necessary  to  state  "  For  Camp  Telephone,  o-bar  magneto  type." 


Fig.  3-23.— TELEPHONE,  CAMP,   AND  CIRCUITS. 


Part 
No. 


Name. 


Case  complete 

Cflver^  complete  with  hinges 

Circuit  (liaRram  frame 

Circuit  (I  iajjram , 

Circiiil  iliagram,  celluloid  cover 

Metal  lia^o  for  case 

Wire  not  I  inn  frame  complete 

\\ir((  IK'II  inj; 

('arryirm  strap,  complete 

Fittmg  and  ring  for  carrying  strap. 


Reference 
No. 


The  iiistniiiiciit  is  made  as  compact  as  ))r;iclical)l(>  and  is  contained  in  an 
oak  ca.se  4.|  i)y  7  by  10  inches  high.  The  loj)  consists  of  a  metal  hinged  cover 
with  circuit  diagram  on  inside,  iicld  rigid  when  closed  by  a  si)ring  sua])  which 
can  be  readily  ii'Iciiscd  by  depi-essing  a  bnllon.     'I'lie  bottom  of  case  is  covereil 

(00) 


Telephony — Camp  Telephone  and  Buzzer. — Chapter  3. 


by  a  ll:inj;ed  piece  ol"  iiietal,  the  llaufie  projecting,'  ap])i-i»xiinatel.v  one-iialf  iiirji 
up  sides  of  case.  Throuf^h  one  side  of  case  are  six  three-eijiiitli  iiicii  liolrs 
which  are  covered  on  the  outside  by  a  close  mesh  metal  screen  held  in  phue 
by  a  metal  frame.  These  apertures  are  for  the  purpose  of  allowing  the  ringer 
to  be  distinctly  heard.  Tlie  case  is  ecpiipped  with  a  sub.stantial,  arljustabh' 
carrying  strap,  each  end  of  which  is  fastened  to  case  by  means  of  hinged  metal 
rings. 


Fig.  3-24.— TELEPHONE,   CAMP,    DISMANTLED. 


Part 
No. 


Name. 


Base  complete 

Coimeotinj;  lilock,  complete  with  binding  post.s. 

Bindinp  post  complete 

Socket  for  h;unl-set  cord  (3  to  a  set) 

Haiul  set  complete 

ITand-set  cord 

Kiuid-set  receiver 

Kaiid-set  receiver  cap 

Hand-set  transmitter 

Hand-set  transmitter  cap 

Battery  case 

Hat  tery-spring  catch 

Hattery  spring  and  support 

Battery,  tungsten,  type  A  (1  unit  per  set) 

Magneto  complete . ." 

Magneto,  crank  handle  for 

Magneto,  permanent  magnet  for 

Magneto,  contact  spring  for 

Magneto,  armature  for 

Magneto,  gear  for 

Magneto,  pinion  for 

Kinger 

Ringer,  pong  for 

Itinger.  hammer  and  armature  for.. 

liinger,  coils  (2  to  a  set ) 

Ringer,  armature  adjusting  screw 

Ca-se  for  hook  switch 

Hook  switch,  complete 

Hook  switch,  contact  springs  for 

Hook  switch,  hook  for 

Posts,  binding,  for  external  battery 


Reference 
No. 


46581°— 17 7 


(91) 


26  Signal  Corps  Manual  No.  3. — Chapter  3. 

A  .small  l'-l)ar  inuiineto  generator,  small  ringer,  induction  coil,  alnmlnum 
chamber  for  the  single  unit  of  tungsten  type  A  dry  battery,  liard  rnl)I)(M-  block 
upon  which  are  mounted  line  binding  posts,  plug  connections  for  the  handset 
used  with  the  instrument,  hook  switch  and  hook  operating  it  and  auxiliary 
battery  binding  posts  are  all  mounted  on  a  common  base  which  may  be  readily 
removed  from  case  after  removing  magneto  generator  crank,  metal  housing 
for  it  and  three  screws  which  extend  through  the  case. 

The  instrument  may  be  operated  with  cover  closed  which  is  highly  advanta- 
geous in  inclement  weather.  To  accomplish  this  there  is  a  suitable  opening  for 
leading  out  the  3-conductor  cord  to  receiver  and  transmitter,  the  two  latter 
being  mounted  in  the  form  of  a  unit,  termed  a  handset.  This  handset  consists 
of  a  transmitter  and  receiver  mounted  on  a  metal  piece  and  is  so  designed 
that  when  the  transmitter  is  normally  placed  to  the  mouth,  the  receiver  is 
automatically  adjusted  to  the  ear. 

The  hook  of  hook  switch  is  so  designed  that  it  protrudes  through  case. 
When  it  is  desired  to  transport  the  instrument  or  to  remove  the  base  upon 
which  is  mounted  all  the  parts  of  the  instrument,  it  is  merely  necessary  to  de- 
press the  hook  and  push  it  toward  the  base.  By  this  arrangement  the  hook  is 
not  only  held  in  the  down  position,  thereby  opening  the  battery  circuit,  but  it 
is  also  protected. 

The  aluminum  chamber  for  housing  the  single  unit  of  tungsten  type  A  but- 
tery is  equipped  with  a  spring  catch  so  located  that  when  upper  hinged  piece  is 
depressed  to  proper  position,  the  battery  compresses  a  helical  spring,  thereby 
insuring  continual  contact.  The  base  is  equipped  with  two  screw  binding  posts 
which  may  be  used  to  conect  leadc  to  an  outside  battery  in  the  event  of  there 
being  no  tungsten  type  A  batteries  available. 

An  aluminum  frame  which  is  supported  on  the  base  previously  mentioned 
forms  a  compartment  for  the  hand.set  when  instrument  is  being  transported. 
When  the  instrument  is  installed  for  a  temporary  period,  unless  in  actual 
operation,  the  proper  place  for  the  handset  is  hanging  .on  the  hook  of  hook 
switch,  there  being  a  ring  on  the  handset  for  this  purpose. 

A  small  screw  driver  which  will  fit  practically  all  the  screws  used  in  the 
construction  of  the  instrument  is  supported  by  the  metal  frame  and  is  furnished 
with  each  instrument.  The  instrument  complete  weighs  approximately  11 
pounds. 

TiiK  si;i;\  i(  K  i!i'/./Ki;. 

The  buzzer  is  strictly  a  portable  instrument  and  is  issued  to  troops  in  the 
held  for  use  in  connection  with  all  kinds  of  lines  of  conununication.  It  may  be 
used  as  a  teleplione  or  for  sending  customary  IMorse  or  Continental  ('ode  signals 
and  for  that  reason  it  is  .specially  adapted  for  field  use. 

W 111 'II  it  becomes  impracticable  to  transmit  messages  telephonically,  due  to 
line  becoming  impaired  or  for  other  reasons,  the  usual  telegraphic  signals  can  be 
transmitted  and  are  received  in  distant  telephone  receivers  in  the  form  of  a 
high-pitched  hum,  somewhat  similar  to  radiotelegraphic  signals.  These  sig- 
nals have  been  exchanged  between  two  of  these  instruments  after  the  line  wire 
had  been  sevt^red,  both  the  ends,  however,  being  slightly  grounded. 

The  service  buzzer,  which  is  the  latest  approved  instnniu>iit  of  this  type  of 
apparatu.s,  replaces  the  field  buzzer,  the  cavalry  buzzer,  and  the  field  artillery 
telephone  anri  hereafter  is  the  .standard  issue  where  the  above-enumerated 
obsolete  apparatus  is  involved. 

In  the  first  i)art  of  this  chapter  is  explained  how  a  circuit  t>f  high  E.  M.  F.  is 
obtained  by  means  of  two  coils  of  wire  wound  on  a  soft  iron  core  in  connection 

(92) 


Telephony — Camp   Telephone  and  Buzzer. — Chapter  3. 


27 


with  the  telephone.  Thi.s  method  may  he  tei'med  mutual  induction  and  i.s  em- 
ployed in  the  service  buzzer.  A  high  E.  II.  F.  can  be  obtained  by  means  of  one 
coil  of  wire  wound  on  a  .soft  iron  core,  the  latter  method  being  termed  .self- 
induction.  In'  order  that  operation  of  service  buzzer  may  be  clearly  understood, 
the  theory  of  the  field  buzzer  will  first  be  explained. 

The  principle  upon  which  the  original  firlil  buzzer  operates  depends  upon  the 
effects  of  self-induction;  i.  e.,  the  comparatively  high  self-induced  voltage  devel- 
oped at  the  terminals  of  an  electromagnet  (coil  with  iron  core)  when  the  cur- 
rent through  the  circuit  is  suddenly  interrupted.  The  interruptions  are  auto- 
matically produced  by  a  circuit  breaker,  which  is  described  later.  During  the 
interval  of  time  required  for  the  current  to  reach  its  maximum  value,  the  field 
of  force  expands  in  direct  proportion  to  the  current  strength  until  it  also 
reaches  maximum  value.  The  current  strength  being  kept  constant,  the  mag- 
netic tield  is  of  constant  value.  Any  variation  in  current  strength  produces  a 
corresponding  variation  in  the  strength  of  the  magnetic  field;  therefore,  when 
the  circuit  is  broken  and  the  current  rapidly  falls  to  zero  the  field  of  force  also 
collapses  and  disappears.  The  energy  furnished  by  the  current  and  stored  up 
in  the  magnetic  field  is  thus  returned  to  the  circuit  and  tends  to  sustain  the 
original  current,  as  is  noticed  by  a  bright  spark  appearing  at  point  of  break. 


K 


\^ 


mm 


R 


B 
■o-lllll  ill 


Fig.   3-25.— BUZZER,    FIELD,    SIMPLIFIED   CIRCUIT. 

On  "  make,"  then,  the  whirls  spring  out  from  and  cut  the  wire,  inducing 
therein  a  current  opposed  in  direction  to  inducing  current.  On  "  break  "  the 
whirls  collapse,  again  cutting  the  wire  and  inducing  therein  a  current  having 
same  direction  as  inducing  current.  The  phenomena  resulting  from  such  cutting 
of  a  wire  by  magnetic  lines  of  force  is  called  self-induction. 

When  the  circuit  contains  a  coil,  the  above-noted  effects  of  self-induction  are 
much  greater.  If  the  coil  contains  an  iron  core  the  effects  of  self-induction 
are  still  more  i)ronounced. 

To  make  clear  the  action  of  the  buzzer,  let  us  consider  the  diagram  (lig. 
3-25)  : 

B  is  a  battery  of  five  dry  cells;  K  is  a  ki\v  for  making  and  breaking  the 
circuit ;  E  an  electromagnet ;  It  a  telephone  receiver. 

When  the  key  is  closed  there  is  a  rush  of  current  which  readn-s  its  maxi- 
mum strength  almost  instantly.  Simultaneously  there  is  built  up  a  magnetic 
field  of  forie  around  the  elec-tromagnet.  Now,  if  the  key  be  opened,  a  pro- 
nounced click,  of  momentary  duration,  is  heard  in  the  receiver,  which  is  caused 
by  a  .self-inducod  current  of  high  E.  M.  F.  produced  by  the  collapse  of  the  mag- 
netic field  around  the  coil.  This  induced  current  wouhl  spark  a<-ross  break 
at  the  key  if  there  were  not  an  alternate  complete  circuit  through  the  re- 
ceiver. 

(93) 


28 


Signal  Corps  Manual  No.  3. — Chapter  3. 


The  more  rapidly  the  circuit  is  made  and  brolven  by  closing  and  opening 
tlie  key,  the  greater  the  rapidity  with  which  clicks  in  telephone  follow  one 
another,  until,  if  the  interruptions  recur  sufficiently  often,  the  sounds  in  the 
receiver  appear  to  be  almost  continuous. 


K 


^" 


E 


M 


B 


h|i|i|i|i 


trnf" 


Fig.   3-26.— BUZZER,    FIELD,    SIMPLIFIED    CIRCUIT   WITH    INTERRUPTER. 

If  we  introduce  an  automatic  interrupter  into  the  circuit  (fig.  3-26),  a  loud 
buzzing  sound  is  heard  in  the  receiver  whenever  the  key  is  closed,  and  the 
dot  and  dash  of  the  Morse  alphabet  are  thereby  produced  by  making  short 
and  long  contacts  with  key. 

The  action  of  the  interrupter  or  circuit  breaker  is  as  follows : 

When  the  circuit  is  made  by  closing  the  key  K,  the  current  flows  through 
coils  of  the  electromagnet  E,  magnetizing  the  iron  core  JA,  which,  in  turn,  at- 
tracts armature  A.  As  soon  as  the  armature  is  withdrawn  from  contact  S 
the  circuit  is  broken ;  as  a  result,  the  core  becomes  demagnetized  and  arma- 
ture A  springs  back  against  S\  thus  again  closing  the  circuit.  This  action  con- 
tinues so  long  as  key  K  is  kept  closed. 

If  instead  of  interrupter  we  substitute  therefor  a  transmitter  (fig.  3-27).  then 
when  the  key  is  closed  current  flows  from  +  side  of  the  battery  through  the 
coil  to  the  lower  disk  (stationary)  of  ti'Jinsmitter,  through  loosely  packed  carbon 
granules  to  upper  disk  (movable)  which  is  attached  to  the  diaphragm,  to  key, 
to  —  side  of  battery. 


7 


^  Upper  disc 
Lower  disc 
■a 


mm 


s 


B 

llho- 


Fig.   3-27.— BUZZER.    FIELD,    SIMPLIFIED    CIRCUIT   WITH    TRANSMITTER. 

E.xcept  wlien  this  circuit  is  first  nuide,  there  is  no  evidence  of  .self-induction 
in  the  circuit  until  the  transmitter  is  spoken  into,  tlien  the  sound  waves  of  the 
voice  striking  the  diaplu'agm  cause  it  to  vibrate.  The  carbon  granules  between 
tlie  carlion  disks  are  thus  subjected  to  varying  pressure;  this  causes  a  variable 
n^sistiuice  in  the  circuit,  and  the  resulting  current  is  a  pulsating  one  (uniform 
ill  dirfftion,  but  varying  in  strcngtli).  The  ell'ect  of  the  varying  current  i)assing 
through  the  circuit. is. to  increa.se  and  decrea.se  the  field  of  force  built  up  around 


(04) 


Telephony — Camp  Telephone  and  Buzzer. — Chapter  3. 


29 


tho  wire.     This   changing  field   of   loi-cc   in    iiiin    inuchicis   iIm-  ctTpfts   of  sHf- 
inductidii,  and  tliese  effects  are  i»artk'ularly  noticaljlc  in  euil  h'. 

Tli«'  inductive  property  of  the  coil  is  thus  enipioywl  to  uuKnient  the  com- 
l)artively  weatc  primary  current  to  (»ne  of  hifih  10.  M.  F.,  which  intensifies  the 
vibration  of  tiie  receiver  diapln-a^ni,  tliese  vibrations  beinj:  receive<l  by  the  ear 
as  articulate  speech. 


^^^s 


B 


mmf^ 


o        o 


Line  to  distant  station 


Fig.  3-28.— BUZZER,    FIELD,    SIMPLIFIED    CIRCUIT    WITH    TRANSMITTER    AND   INTER- 
RUPTER. 

The  sounds  thus  produced  are  not  as  loud  as  those  produced  by  the  interrupter 
even  though  the  same  number  of  cells  are  used,  for  the  reason  that  in  the  latter 
case  the  current  is  completely  interrupted  (circuit  broken),  whereas  in  the  case 
of  the  talking  circuit,  current  is  always  flowing,  but  is  varied  in  strength; 
therefore  the  resulting  field  of  force  never  reduces  to  zero,  the  cutting  of  the 
wire  is  consequently  less,  and  the  effects  of  self-induction  are  diminished. 

If  we  now  combine  the  two  circuits  described  above  in  one  diagram  we  have 
the  simplified  buzzer  diagram  which  is  shown  in  (fig.  3-li8). 


Tdegraph  Line 


Condervser 


Buzier 


Condenser 


o 

Buzzer 


Fig.   3-29.— BUZZERS.   CONNECTED   TO    A   TELEGRAPH    LINE. 

An  examination  of  this  figure  shows  that  the  only  change  made  is  th»'  intro- 
duction of  two  terminal  binding  posts,  one  of  which  is  connected  to  the  line. 
the  other  to  the  ound.  If  a  similar  instrument  is  coniuH-te<l  at  the  distant 
stations,  the  currents  traversing  home  receiver  also  pass  through  distant 
receiver. 


O.l) 


30  Signal  Corps  Manual  No.  3. — Chapter  3. 

The  utilization  of  existing  telegraph  lines  as  a  part  or  the  whole  of  a  circuit 
for  buzzer  and  telephone  working,  at  the  same  time  not  interfering  with  the 
use  of  the  wire  for  Morse  working,  may  be  etfected  by  using  condensers  inter- 
posed between  the  line  and  the  buzzer.     (See  fig.  3-29.) 

The  pulsations  of  the  ordinary  INIorse  sending  are  comparatively  slow.  The 
condensers,  therefore,  act  as  a  very  large  resistance,  and  no  appreciable  effect 
will  be  noticed  in  the  telegraph  line. 

The  very  rapid  pulsations  produced  by  the  buzzer  or  transmitter,  however, 
will  permit  of  transmission  from  one  buzzer  to  the  other  with  little  diminution 
of  sound. 

Figure  3-30  shows  the  circuits  of  the  service  buzzer.  It  will  be  noted  that 
with  the  field  buzzer  if  a  line  of  low  insulation  resistance  is  utilized  a  heavy 
drain  on  the  batterv  will  ensue,  due  to  battery  being  connected  to  the  line, 
while  with  the  service  buzzer  under  like  conditions  a  heavy  drain  will  not 
exist,  due  to  battery  being  connected  in  a  local  circuit  which  does  not 
physically  connect  with  line.  It  will  also  be  noted  that  a  condenser  which 
can  be  cut  out  by  means  of  a  short-circuiting  switch  is  contained  in  the  instru- 
ment and  connected  in  series  with  the  line.  This  condenser  is  for  use  when 
it  is  desired  to  use  an  existing  telegraph  line.  (See  fig.  3-29.)  Two  units 
of  tungsten  type  A  dry  battery  are  used  with  the  service  buzzer  for  furnishing 
the  necessary  primary  current,  both  being  in  circuit  when  sending  telegraphic 
signals,  and  one  only  being  in  transmitter  circuit  for  telephone  communica- 
tion. 

The  circuits  of  the  service  buzzer  may  be  classed  as  follows: 
Primary  sending  circuit — telegraph. 
Secondary  sending  circuit — telegraph. 
Receiving  circuit — telegraph. 
Primary  sending  circuit — telephone. 
Secondary  sending  circuit — telephone. 
Receiving  circuit — telephone. 

These  circuits  may  be  traced  as  follows,  i-eference  being  made  to  figure  3-30 : 

PUIMAKY   SENDING   CIRCUIT TELEGRArH. 

S.  P.  D.  T.  knife  switch  marked  "  Sio "  must  he  closed  on  side  marked 
"buzzer."  Upon  depressing  key  K,  circuit  is  as  follows:  Positive  end  of  bat- 
tery, through  primary  of  induction  coil,  to  A  to  B,  contact  1  of  key,  lever  of  key, 
contact  2,  vibrator,  to  negative  end  of  battery. 

SECONDARY    .SENDING    CIRCUIT TELEGRArH. 

/S.  P.  D.  T.  knife  switch  marked  "  Siv  "  is  closed  on  side  marked  "  buzzer."  An 
A.  C.  current  of  high  E.  M.  F.  is  induced  in  secondary  winding  of  induction  coil 
by  interrupted  current  in  primary  and  its  path  is  as  follows:  G,  earth  or  one 
side  of  line  (if  metallic  circuit  is  used);  "receiving  circuit,  telegraph"  of 
distant  buzzer,  other  side  of  line,  L,  contact  1  of  key  (key  is  depressed),  li,  A, 
otiicr  side  of  secondary  winding  of  induction  coil. 

RECEIVING   CIRCUIT — TEI-EGRAni. 

»S'.  /'.  />.  7'.  knife  switcii  marked  "Sw"  is  closed  on  side  marked  "buzzer." 
A.  C.  current  of  high  10.  M.  F.  reaches  L  from  distant  instrument  by  one  side  of 
line,  contact  3  of  key  (key  raised),  receiver,  C,  switch  marked  "  Sw,"  G,  other 
side  of  line  to  dislaiit  iiisti-uiiiciit. 

(00) 


Telephony — Camp  Telephone  and  Buzzer. — Chapter  3. 


31 


rui.M.MtY  senium;  ciitci  ri'^ — tki.ki'iium;. 

S.  r.  J).  T.  knife  switch  iiiariaMl  "  Hw  "  i«  closoti  on  side  marked  "  talk  "  ;  fr(»m 
positive  end  of  i)attery  tliroufrli  primary  winding  of  indnction  coil,  to  .1,  to  li, 
tln-ouKh  blade  of  switch  marked  "  .S'lo"  to  C,  through  push-l)Utton  switcli 
marked  "PR,"  throuj,'li  transmitter  t(»  netrative  side  of  one  unit  of  the  luii^rsten 
type  A  battery. 


BOTTOM  VIEW  OF  BACKBOARD  SHOWING  WIRING 


conTI 
<T7~T^ — ^ 

CON. SWITCH --/j,-*^ 

•-'0 


LINE 


.o 


BUZZERj_  SW.     ,    TALK 


SECONDARY 


tWWW-', 


V 


ilk.     I 

_j     Small  c 


J J      0///C 

-  T  I     I  II  (transmit 


{mANSMlm) 


Fig.  3-30.— BUZZER,   SERVICE.   CIRCUITS. 


SKCOXPAItV    sr,>CI>I.\(i   CIUCIIT TEI.EIMHINE. 


.■s'.  /'.  D.  T.  knife  switch  marked  ".S'/r"  is  ch)sed  on  side  marked  "talk."  When 
sound  waves  fall  ni)on  diaphragm  of  transmitter,  an  alternating;  curriMit  of 
hijrli  E.  M.  F.  is  induced  in  .secondary  windin;;  of  induction  coil.  Starting;  with 
secondary  of  induction  coil,  to  (1,  to  earth  or  one  side  of  line  (if  metallic  circuit 
be  used),  throuiL'ii  •' receivin;;-circuit-telephone  "  of  distant  instrument,  return- 
ing on  other  side  of  line,  to  L,  tln'ough  contact  3  of  key  mark»Hl  "A""  (key 
rai.sedt,  to  receiver,  to  C,  to  switch  marke<l  "  iSir,"  through  blade  of  this  switch 
to  B.  to  .1,  to  other  side  of  .secondary  winding  of  induction  cuil. 

IMrCEIVINC    n UCf IT TELKrnoNE. 

^'.  r.  D.  T.  knife  swiuli  mariced  "'Sir"  is  closed  on  side  marked  "talk."  An 
alternating  current  of  high  E.  SI.  F.  induced  in  the  secondary  wimling  of 
induction  coil  in  distant  instrunienl.  reaches  buzzi-r  over  outside  lin««,  to  I.. 
thence  to  contact  3  of  key  marked  "  A',*'  to  re«'i'iver.  to  T.  to  switch  mark«Ml 
"Sir",  througii  blade  of  this  switch  lo  /{.  to  .1,  through  secondary  winding  of 
induction  coil  to  (7,  to  earth  or  line  (if  metallic  circuit  be  u.sed).  to  distant 
buzzer. 


(97) 


32 


Signal  Corps  Manual  No,  3. — Chapter  3. 


When  an  existing  telegraph  line  is  utilized,  the  switch  marked  "con  sio" 
should  be  thrown  to  the  "O"  position  in  order  that  the  condenser  "  Con"  will  be 
placed  in  the  circuit. 

Tlie  service  buzzer  is  sliown  in  accompanying  figures  3-31  and  3-32,  it  being 
sliown  dismantled  in  figure  3-32  to  facilitate  preparation  of  requisitions  for 
renewal  parts. 

The  instrument  is  contained  in  an  aluminum  case  fitted  with  a  lunged  cover, 
both  of  wliic-h  are  covered  externally  with  a  russet-colored,  smooth-finish  leather 
which  is  neatly  sewed  and  riveted  in  place.  The  overall  outside  dimensions  of 
the  case  are  approximately  3J  by  5i  by  7*  inches.  The  two  units  of  Tungsten 
type  A  battery  are  contained  in  a  chamber  located  in  the  bottom  and  are 
accessible  without  opening  main  cover,  there  being  an  additional  small  hinged 
cover  in  one  end  of  case  which  is  fastened  securely,  when  closed,  by  a  sub- 
stantial spring  clip,  and  by  a  flap  of  leather. 


Fig.  3-31.— BUZZER,   SERVICE. 


The  instrument  may  be  operated  with  both  covers  closed,  which  is  highly 
advantageous  in  inclement  weather.  To  ac<'omplish  this  there  is  a  suitable 
opening  for  leading  out  the  cords  to  receivci-  and  transmitter,  and  in  main  cover, 
directly  over  the  sending  key,  is  a  round  aperture  which  is  made  moisture-proof 
by  means  of  a  covering  of  extremely  flexible  pigskin.  The  sending  key  can  be 
i-eadlly  operated  through  this  flexible  pigskin. 

The  .sending  key,  induction  coil,  conden.sers.  plug  .jack,  transfer  switch, 
vibrator,  and  binding  pctst.s'for  transmitter  and  receiver  cords  ai*e  mounted  upon 
a  common  base  of  hard  rubber.  Wiring  to  the  component  parts  is  routed  in  the 
underside  of  this  base,  which  is  mounted  in  the  front  of  the  case  above  the  bat- 
tery chamber  previously  mentioned.  In  the  r(>ar  of  the  inslrument  is  a  compart- 
nient  of  leather  for  containing  llie  transniitler,  receiver,  and  cord  for  connect- 
ing them.  At  one  end  of  this  cliiiniber.  neatly  moinited  on  a  liai'd  rubber  strip,  is 
a  .socket  wrench  for  adjusting  the  nuts  which  secure  the  transmitter  and 
i-eceiver  terminals,  also  two  .screw  drivers — one  large  and  one  small — which  are 
so  constructed  that  the  shanks  may  be  inserted  in  the  end  of  socket  wrench, 
thereby  using  socket  w  rcnch  ;is  a  IkiikIIc. 

Invariably  there  is  furnisiicd  willi  (his  instrument  a  two-conductor  cord, 
approximat(!ly  o  feet  long,  one  end  of  wliidi  is  e(|ui|iiied  with  a  substantial  plug 

(08) 


Telephony — Camp  Telephone  and  Buzzer. — Chapter  3. 


33 


similar  lo  (hose  used  in  connection  witli  ii'loplione  switchlxtanls.  At  otlier  end 
one  of  tli(?  conductors  is  e((uipped  with  a  Williams  test  clamp  for  connection  to 
lino,  the  other  conductor  ))einf;  equipped  with  a  Signal  Corps  type  D  jrround 
lod.  The  Williams  tesi  clamp  is  si)  conslructed  that  to  attach  to  line,  it  is 
merely  necessary  to  compress  the  two  principal  parts,  releasing  them  when 
line  has  heen  inserted  in  space  provided.  One  side  of  this  clamp  is  e<piipped 
with  an  11-point  stud  .securely  threaded  to  test  clamp.  These  points  make 
excellent  contact  on  line,  regardless  of  whether  the  line  be  insulated  or  not. 
I5y  tliis  means  a  quick  connection  can  be  made  to  buzzer  wire  or  field  wire 
which  is  insulated,  and  when  the  clamp  is  removed  the  abrasion  to  in.sulation 
is  negligible.  There  is  an  opening  in  the  case  of  buzzer  through  which  the 
plug  is  imserted  when  coimection  is  desired,  and  when  plug  is  .so  inserted,  it 
makes  a  positive  connection  by  means  of  a  substantial  jack  mounted  <in  the 
base  as  i)reviously  indicated. 


Fig.  3-32.— BUZZER,   SERVICF.    DISMANTLED. 


Part 

No. 


Xliiiio. 


Referenco 

Ni. 


1  ]  Case,  complete 

2  Cover  for  ca.-se.  complete 

3  Door,  battery,  complete  witti  hinges 

4  '  Case,  leather,  for  transmitter  ami  receiver. 

5  1  Ciirryini;  st  rap 

6  i  Maiii  cord  witli  terminals 

7  Ground  rod,  type  D 

8  I  Plug 


(Continued  on  next  page.) 
(00) 


34 


Signal  Corps  Manual  No.  3. — Chapter  3. 

Parts  list— Continued. 


Plug,  fiber  cups  for. . . 
Connector,  t  j-pe  A . . . 

Transmitter 

Transmitter,  cap  for. . 

Receiver 

Receiver,  cap  for 

Head  band,  complete 
Base. 


Base,  holding  screws  for 

Induction  coil,  complete 

Condensers  (3  to  a  .set ) 

Condensers,  connect  ing  blocks  for 

Condensers,  short-circuit  switch,  complete. . 

Condensers,  holding  clip 

Jack,  plug,  complete 

Jack ,  spring  for 

Switch,  transfer,  complete 

Vibrator,  complete  (11  pieces) 

Viljrator  screw,  clamp 

Vilirator  screw,  contact 

Vil)rator  tongue  with  platinum  contact 

Key,  sending,  complete 

Key,  lever  for,  without  button 

Key,  supports  and  screws 

Key,  spring  for 

Key,  adjusting  screw  for 

Key,  hard  rubber  button  for ._ 

Binding  post,  complete ." 

Binding  post,  screws  and  washers  for 

Screw  dri\er,  large 

Screw  driver,  small 

Handle  for  screw  drivers,  and  wrench 

Battery,  Tungsten,  type  A  (2  imits  to  a  set). 
Battery  spring  and  support 


18 


The  case  has  an  adjustable  carrying  strap,  one  end  of  which  is  equipped  with 
a  snap  connection,  the  other  end  being  sewed  to  hinged  fitting  on  case.  Tlie 
instrument,  Inchiding  carrying  strap,  type  D  ground  rod,  Williams  test  damp, 
plug  and  H-foot  cord,  weighs  approximately  5  pounds,  and  full  directions  ft)r 
operation,  together  with  a  circuit  dhigram,  are  attaclied  to  tlie  inside  of  main 
cover. 

Figure  3-33  shows  tlie  circuits  employed  in  sending  and  receiving  Morse 
signals  by  means  of  service  buzzers.  It  will  be  noted  tluit  a  single  conductor  is 
used  to  connect  the  two  instruments,  and  that  the  earth  is  used  for  other  con- 
ductor of  tlie  circuit.  This  is  the  customary  manner  <if  connecting  two  or  more 
service  l)uzzers  in  tlie  field. 


SENDING  STATION  = 


Ground  Rod 

RECEIVING  STATION 


Fig.  3-33.— BUZZER.   SERVICE,   SENDING    AND    RECEIVING    MORSE  SIGNALS,   CIRCUITS 

EMPLOYED. 


(100) 


ClI.M'TF.R  4. 

CABLE  AND  CABLE  SYSTEMS. 

The  cables  provided  Ity  the  Sijriial  Corps  are  oC  two  fieneral  classes,  namely, 
submarine  and  sultlerranean.  The  two  general  classes  may  each  be  dividcil  into 
two  classes,  depending:  upon  the  insulation  used — whether  rubber  coiniKUiiid 
or  paper.  As  the  development  of  the.se  cables  has  been  alonK  different  lines,  they 
will  be  described  under  separate  headings. 

SUBMARINE    CABLES. 

The  first  successful  submarine  cables  employed  f?utta-percha  as  an  insulating 
medium.  This  compound  is  subject  to  rapid  deterioration  when  exposed  to  air. 
and  for  that  reason  such  cable  nmst  be  kept  submersed  at  all  times. 

The  general  use  of  India  rubber  as  an  insulator  in  subterranean  and  aerial 
power  cable  work  led  American  manufacturers  to  the  development  of  this  com- 
pound as  an  insulator  for  submarine  cable,  and  many  hundreds  of  miles  of  deep- 
sea,  rubber-insulation  submarine  cable  have  been  successfully  laid  and  operated 
by  the  Signal  Corps. 

While  it  is  frequently  stated  that  rubber  compounds  used  in  deep-sea  cable 
work  are  not  materially  affected  by  exposure  to  air  for  a  considerable  period, 
the  Signal  Corps  has  found  it  impracticable  to  store  this  class  of  cable  without 
submerging,  although  rubber  is  undoubtedly  vastly  superior  to  gutta-percha  in 
this  respect. 

The  most  serious  problem  in  the  design  of  rubber  insulation  cables  for  tele- 
phone work  is  due  to  the  mechanical  characteristics  of  the  compound.  Since 
the  cable  must  be  made  up  in  twisted  pairs  in  order  to  avoid  trouble  from 
induction,  a  tensile  strain  will  tend  to  cause  the  conductors  of  the  twisted 
pairs  to  press  through  the  compound  at  points  of  crossing,  lowering  the  insula- 
tion and  eventually  interrupting  conununication.  This  trouble  is  most  marked 
in  the  larger  types. 

The  corrosive  action  of  sulphur  used  in  the  rubber  compound,  on  the  copper 
conductors  is  a  troulile  which  is  dilhcult  to  eradicate  completely.  Another  dith- 
culty  which  is  connnon  to  both  rubber  and  gutta-percha  lies  in  the  high  capacity 
which  results  from  the  use  of  either  of  these  forms  of  dielectric.  On  short 
lengths  of  cable  this  objection  is  not  serious,  but  the  fact  tiiat  25  miles  of 
ordinary  rubber-covered  twisted  pair  is  the  limit  of  audible  conversation  nmst 
frequently  be  taken  into  consideration  in  designing  cable. 

As  a  re.sult  of  many  years  experience  in  harlutr  cable  maintename  the  modi- 
fied conniiercial  types  of  cable  indicated  herein  have  been  adopted. 

While  the  use  of  rubber  in  this  class  of  cables  has  been  gen»'rally  abandoned 
in  favor  of  paper,  the  Signal  Corps  has  retained  this  insulation  for  cables  not 
exceeding  six  pairs  in  size.  It  is  thought  that  in  the  smaller  cables  there  is  a 
slight  advantage  in  simplicity  of  repair  of  rubber,  and  no  markt^l  economy  is 
gained  in  the  use  of  paper  insulation.  For  cables  from  five  pairs  upward,  thera 
are  many  advantages-  in  the  adoption  of  the  paper  insulation. 

(101)  1 


2  Signal  Corps  Manual  No.  3. — Chapter  4. 

RUBBER   INSULATION    SUBMARINE  CABLES. 

The  conductors  of  these  cables  invarial)ly  consist  of  seven  strands  of  annealed 
copper  wire,  28.5  or  20.1  mils  diameter,  tinned  to  prevent  as  far  as  practicable 
the  corrosive  action  of  sulphur  in  the  rubber.  Each  conductor  is  insulated  as 
follows : 

First.  With  a  coatinc  of  fine  Para  rubber  to  a  uniform  thickness  of  one  sixty- 
fourth  of  an  inch. 

Second.  With  a  compound  containing  either  30  or  40  per  cent  of  fine,  unre- 
covered  Para  rubber  to  a  uniform  diameter  of  thirteen  sixty-fourths  of  an  inch, 
the  compound  being  applied  seamlessly. 

Third.  With  a  .SO  per  cent  rubber  compound,  conforming  to  the  requirements 
of  Signal  Corps  specification  to  a  diameter  of  nine  thirty-seconds  of  an  inch. 
The  insulation  is  then  covered  with  a  layer  of  best  cloth  tape  saturated  with  an 
approved  rubber  compound,  and  put  on  with  a  double  lap. 

It  has  been  claimed  that  one  layer  of  rubber  compound  instead  of  three  is 
more  satisfactory,  consequently  in  future  one  layer  only  of  either  40  per  cent 
or  30  per  cent  compound  will  be  applied  in  the  manufacture  of  some  of  these 
cables. 

In  multiple  conductor  cables,  two  of  the  conductors  are  twisted  together 
and  all  conductors  are  grouped  together  in  such  a  manner  that  the  finished 
core  will  be  cylindrical.  The  core  is  then  given  two  sufficient  servings  of  best 
India  jute  roving,  which  has  been  previously  steeped  in  a  strong  solution  of 
cutch  and  dried.     The  jute  serving  is  put  on  in  reverse  layers. 


TYPE  50 


,^f^~\ 


TV:£E  56 

Fig.  4-1.— CABLE,    SUBMARINE,    RUBBER    INSULATION. 

The  core  of  the  cable  is  then  armored  by  having  a  number  of  steel  wires 
wound  spirally  about  it.  The  lay  of  the  armor  wire  is  left  hand,  the  length 
of  such  lay  being  equal  to  10  times  the  diameter  of  the  cable,  measured  over 
the  arnioi-  wires.  Where  a  double  ai-nior  is  applied  the  outer  has  a  right-hand 
lay.  The  diameter  of  the  armor  wires  varies  from  144  mils  for  1-conductor 
cable  to  220  mils  for  12-con(luctor  cable.  They  are  invariably  heavily  gal- 
vanized and  re(iuinMl  to  meet  certain  tests  in  this  respect. 

The  completed  cable  is  then  served  with  two  layers  of  India  jute  yarn,  one 
being  in  reverse  direction  to  that  of  tlu'  oilier,  the  cal)le  being  run  through 
hot  asphalt  conii)ouM<i  allcr  jtiacing  each  <»('  the  nhov(>  layers  of  jute.  To  pre- 
vent sticking,  the  com]ilclcd  cable  is  then  nni  through  jiowdercd  chalk  (whit- 
ing) or  other  aj»prov«'d  impali)ably  ijowdercd  rock. 

The  following  table  gives  the  i)rincii)al  (•haracteristi<'S  of  the  latest  ai)i)roved 
tyiK's  of  rul)b('r  insulation  cable  uscmI  by  the  Signal  Corps  lor  .submarine  con- 
tiect  ions    (sec  tig.  4-1  ). 

(102) 


Cable  and  Cable  Systems. — Chapter  4. 


For  list  of  all  types  ol'  rui)lH'r  insiilalinn  cnhlcs  iIimi 
niariiio  foiiiioftioiis,  see  chapter  8  of  this  Manual  : 


ia\('   licci)    lb 


fur  sill)- 


Conductor. 

Per  statute  milf. 

^^.^ 

Num- 
ber 
of  con- 
ductors. 

Twfated 

Diameter 
over  insu- 

Armor, 
diameter 

Lay  of 
armor  not 

Capac- 

Resist- 

Length 
on  reel 
unless 

Diameter 

pairs. 

Number 

of  each 

lation. 

in  mils. 

more 
than — 

ity  not 

ance 

otherwise 

of  strands 

strand  in 

more 

of  cop- 

specified. 

mils. 

than— 

per. 

Inch. 

Inches. 

M.F. 

Ohnu. 

F',t. 

50 

1 

0 

7 

28.5 

144 

12 

.  5 

9.7 

10,  .y.() 

51 

2 

1 

7 

28.5 

144 

12 

.  5 

9.7 

10,  .>^J 

52 

4 

2 

7 

28.5 

162 

14 

.  5 

9.7 

10,  .'.DO 

53 

6 

3 

7 

28.5 

204 

10 

.  5 

9.7 

5, 2s(j 

54 

8 

4 

7 

28.5 

204 

10 

.  5 

9.7 

5,2S() 

55' 

10 

5 

7 

28.5 

0  4 

229 

18 

.  5 

9.7 

2,040 

50 

12 

6 

" 

28.5 

i! 

229 

18 

.5 

9.7 

2,640 

Note.— Armor  shall  have  a  left-hand  lay. 

Kuhher  insulation  cahle  may  he  furui-slied  in  douhle  armor  if  installation 
is  requiretl  iii  unusually  rocky  localities. 

PAPKK-lNSrL.VnO.V     SlH.MAKl.NK    CAIU.KS. 

The  necessity  for  an  insulation  which  would  he  free  from  the  ohjections 
noted  for  ruhher  and  the  more  numerous  ohjections  to  gutta-percha  led  to 
the  development  of  the  paper-insulation  cahle.  In  case  of  a  puncture  of  the 
sheath  the  paper  core  swells  and  dampness  tends  to  work  hack  but  a  very 
short  distance.  This  cable  is  free  from  all  of  the  objections  cited  for  rubber 
and  gutta-percha. 

The  conductors  are  insulated  with  two  wraps  of  dry  manila  paper  of  such 
character  and  iu  such  a  manner  as  to  meet  specified  capacity  and  insulation 
requirements.  The  insulating  manila  paper  is  plain  in  color  for  one  con- 
ductor of  each  pair  and  colored  for  the  other.  The  core  of  the  cahle  is  "  laid 
up"  in  twisted  pairs,  each  pair  having  four  twists  per  foot.  These  pairs  are 
"  laid  up  "  in  successive  layers,  each  successive  layer  being  wound  in  reverse 
direction  to  the  precetling  layer,  making  a  complete  turn  in  fntm  IS  t(»  36 
inches.  The  whole  core  is  served  with  a  covering  of  heavy  manila  paper 
and  encased  in  a  lead  sheath,  the  thickness  of  which  vari»'s  with  the  size  of 
the  cahle.  Jute  and  armor  are  then  applied  in  manner  previously  describe*.! 
in  this  chapter. 

The  following  table  gives  the  ))rincipal  cluiracteristics  of  the  latest  api)roved 
types  of  paper-insulation  cable  used  by  the  Signal  Corps  for  sul)marine  con- 
nections.    ( See  fig.  4-2. ) 


/■OuterJute 


TYPES      320    TO   327    INC 


Fig.  4-2.— CABLE,  SUBMARINE,  PAPER  INSULATION 


(103) 


4  Signal  Corps  Manual  No.  3. — Chapter  4. 

For   list   of  all    types   of  paper-iusiilatinn   cables   that   have   been   used   for 
submarine  connections,  see  chapter  8  of  this  manual. 

Paper  insulation,  lead  covered  and  armored  cable. 


Type 
No. 

Number 
of  con- 
ductors. 

Size  of 
conduc- 
tor, B. 
andS. 
gauge. 

Size  of 

armor, 

B.  W.  G. 

gauge. 

Per  statute  mile. 

Capacity. 

Eesistance 
of  copper. 

Weight. 

320 
321 
322 
324 
325 
326 
327 

10 
20 
30 
40 
50 
60 
100 

19 
19 
19 
19 
19 
19 
19 

6 
4 
4 
4 
4 
4 
4 

Microfarads. 
0.10 
.10 
.10 
.10 
.10 
.10 
.10 

Ohms. 
45 
45 
45 
45 
45 
45 
45 

Pounds. 
20,400 
27,900 
29,880 
35,805 
39,115 
47,355 
57, 750 

No*E. — All  in  twisted  pair,  double  wrap,  dry  paper, 


Reserve  reels  of  paper-insulation  caltle  are  provided  in  all  coast-defense 
commands  having  important  submarine  cable  installations.  Ordinarily  all  sub- 
marine cables  are  laid  and  repaired  by  the  personnel  of  one  of  the  Signal  Corps 
cable  ships.  In  the  event  of  the  cable  ship  not  being  available,  the  reserve 
cable  can  be  laid  to  replace  one  that  becomes  unserviceable,  by  means  of  a  tug 
and  lighter,  one  or  both  of  which  can  usually  be  obtained  in  the  immediate 
vicinity. 

The  latter  action  is  taken  only  when  the  exigencies  of  the  service  require 
communication,  which  has  been  interrupted,  to  be  established  before  the  cable 
ship  can  be  sent  to  make  the  necessary  repairs. 

Subterranean    Cables. 

The  manufacture  of  paper-insulation  cable  has  been  perfected  to  such  a  degree 
that  the  cost  of  this  class  of  cable  is  far  below  that  of  the  rubber-insulation 
type.  Subterranean  cable  usually  supplied  for  communication  purposes  is  paper 
insulation,  lead  sheathed  but  not  armored,  It  being  understood  that  suitable 
conduits  for  the  installation  will  be  provided.  Where  it  is  impracticable  to 
furnisli  a  conduit,  lead-covered  and  armored  cable  is  furnished  (regardless  of 
insulation),  and  the  cable  is  laid  in  a  trench  a])proximately  2  feet  deep  and 
then  covered  with  earth.  The  manufacture  of  rubber-insulation  subterranean 
cable  and  paper-insulation  subterranean  cable  are  so  similar  to  t-ables  with 
same  insulation  for  submarine  work  previously  described  in  this  chapter  that 
detailed  description  would  be  superfluous.  Suffice  it  to  say  that  invariably 
cable  for  submarine  work  Is  supplied  with  an  armor  regardless  of  nature  of 
insidallon  and  in  addition  a  lead  sheath  if  the  insulation  be  paper,  while  cable 
fi>r  subterranean  use  is  armored  only  when  it  is  intended  that  it  shall  be 
ti<'nclied  or  placed  in  an  exposed  location. 

I)(iul)le  lead-covered  cable  may  be  supi)lie(l  Un-  iiislnllalioii  in  inarslics  or 
.similar  locations  where  mechanical  damage  is  uiilik(>ly. 

The  following  tables  indicate  the  latest  aiiproved  tyiics  of  sublcrrancan  cables 
used  for  lines  of  communication. 

For  comiilete  lists  <if  cables  that  have  been  used  lor  subtci-rancan  work,  see 
chapter  8  of  this  manual, 


(104) 


Cable  and  Cable  Systems. — Chapter  4. 

Ruhlx  r  iihsuliitioii  !siil>tcn(tit>(in  ctthlc 
(See  fig.  4-.3.] 


Tvpe 
No. 

Nnmtx?r 
of  con- 
ductors. 

Number 

and 

size  of 

strands 

B.  and  S. 

gauge. 

Diameter 
over  insu- 
lation 
(rubber). 

.\rmor. 

15.  \v.  <;. 

gauge. 

Weiglit 
per  mile. 

Length 
on  reel. 

213 
214 

215 
216 
217 
218 
251 

2 
6 

12 
24 
12 
24 
2 

7-24 
7-24 

7-24 
7-24 
7-24 
7-24 
1-18 

Inch. 
5/32 
5/32 

5/32 
5/32 
5/32 
5/32 
4/32 

Pounds. 
3,000 

mu. 

,  ! 

Feel. 
1,000 
1,000 
1,000 
1,000 
1,000 

9,200 

11,100 
14,785 
18,800 
26,900 

14 
9 

(') 

>  Steel  tape. 
Note. — .\llin  twisted  pair,  with  J-inch  lead  sheath,  except  the  type  251,  which  has  a  1/32-iiich  lead  slieatb. 

Armcr  ':c'r':{fel  f/:rv. :n30In  ihJrk 


TrPE-  251 


TYPE    217 
Fig.  4-3.— CABLE,    SUBTERRANEAN,    RUBBER    INSULATION. 

I'aprr  insula fioii.  had-corcn d  lalilc. 
[See  fig.  4-4.] 


Tviw 
No. 


401 
402 
403 
404 
405 
406 
407 
408 
409 


Designation. 


Conductor, 

diameter  of 

each  strand 

in  mils. 


Thickness 
of  lead 
sheath. 


-Vpproxi- 
raate  out- 
side diam- 
eter. 


10-pair. . 
15-pair. . 
20-pair. . 
25-pair. . 
30-pair.  . 
40-pair- . 
50-pair . . 
75-pair. . 
lOO-pair. 


3/32 
3/32 
3/32 
3/32 
3/32 
7/64 
7/64 
7/64 
7/64 


Inches. 
0.722 
.797 
.872 
.922 
.982 
1.113 
1.208 
1.44.3 
1.638 


Weight  per 

statute 

mile. 


Pounds. 
5,370 
6,193 
7,054 
7,693 
8,416 
11,083 
12,445 
15, 829 
18,860 


Weight  per 

1.000  feet  of 

cable  and 

reel. 


Pou 


nds. 
1,1S6 
1.368 
l,.i58 
1,700 
1,860 
2,448 
2,750 
3,497 
3,967 


Note. — A]  in  twisted  pair,  double  wrap,  dry  paper. 


(105) 


Signal  Corps  Manual  No.  3. — Chapter  4. 

Paper  insulation,  double  lead  covered  cable. 
[See  flg.  4-4.] 


Type 
No. 

Number 
of  con- 
ductors. 

Size,  B. 

and  S. 
gauge. 

Per  statute  mile. 

Capacity. 

Resistance 
of  copper. 

Weight. 

312 
313 
314 
315 
316 
317 

10 
20 
30 
50 
60 
100 

19 
19 
19 
19 
19 
19 

Microfarads. 
0.10 
.10 
.10 
.10 
.10 
.10 

Ohms. 
45 
45 
45 
45 
45 
45 

Pounds, 
15,100 
18,400 
21,100 
23,000 
24, 400 
26,400 

/Ltad 


TYPES     320   TO-327   INC. 

Fig.  4-4.— CABLE,   SUBTERRANEAN,    PAPER    INSULATION. 

It  will  he  notetl  that  paper  insulatimi  cable,  lead  covered  and  armored,  may 
he  used  either  for  .suhni:irine  w()rk  or  .siihterranean  w(»rk  wliere  it  is  intended 
that  the  cahle  he  trenched. 

I'OWKK   CAULt. 

(,'ai)lesu.se(l  for  transnuttinji  jiower  such  as  are  necessary  in underjiround  lijiiit- 
ins  and  power  systems,  the  charfring  and  dischurjiing  of  storage  hatteries  or  any 
use  where  Uie  strength  of  current  employed  is  large  as  comiiiircd  with  (hat  of 
a  lelejdione  or  telegra]ih  circuit,  are  termed  jiower  cahle.s. 

Power  cahles  employing  pajter  insulation  are  (piile  extensively  used  in  the 
connnercial  world,  hut  it  is  helieved  that  all  things  considered  (he  ruhher  insu- 
lation cahle  is  more  .satisfactory  for  this  ])urp()se,  mid  lor  (hat  icasoii  ;dl  power 
cahles  furnished  hy  the  Signal  Corps  are  of  (he  Inlter  class. 

Tlie  rule  which  pre.scrihes  armor  for  siililei-raueiin  coniiMuiiicalion  cahles 
laid  in  trench  aiijtlies  also  for  the  installation  of  ixtwer  cahles. 

The  following  tahle  indicates  jutwcM*  cahles  usually  carried  in  s((M-k  hy  (he 
Signal  CV»rps.  For  complete  list  of  power  cahle  that  can  he  supi)lied,  .^^ee  chapter 
S.  It  is  imi)()rtant  to  note  that  these  power  cahles  may  he  furnished  in  a 
number  of  sizes   and    that   ea<h   size   may   he  single  or   duplex,   also   that  any 

(106) 


Cable  and  Cable  Systems. — Chapter  4.  7 

of  the  cables  can  be  supplied  with  either  an  outer  braid,  lead  shealh,  or  lead 
sheath  and  armor. 

Rubber  insula t tan  power  cable. 
[See  Fii;.  4-.V) 


Type  numbers. 

Area 
circu- 
lar 
mils. 

Num- 
ber of 
strands 
per  con- 
ductor. 

Diam- 
eter of 
single 
wires. 

Resist- 
ance of 

con- 
ductor 
per 
1,000 
feet, 
68°  ]•'. 

Length  on  reel. 

Diam- 
eter of 
armor 
wires. 

Sin- 
gle 
L.  C. 

Du- 

Du- 
plex 

L.  r. 

and 
ar- 
mor- 
ed. 

Thick- 
ness of 
wall  of 
nibtjer 
insula- 
tion. 

Single 
braided 

and 
single 

L.  C. 

Duplex  Thick- 
L.  C.    ness  of 
and       lead, 
duplex ' 

ar- 
mored. 

622 
623 
624 
625 
626 
627 

642 
643 
644 
645 
646 
647 

662 
663 
664 
665 
666 
667 

6.  .530 
10, 3S0 
16,510 
26, 250 
33.100 
41,740 

Mils. 
80.81 
102.0 
48.6 
61.2 
68.8 
77.2 

1.586 
.9972 
.6271 
.3944 
.3128 
.2480 

I-nch. 

31 

Feet. 
2,000 
1,500 
1.500 
l,oOO 
1,500 
1,500 

Feet.       Inch. 
1.000 

1.000            i 
1,000  i         i 
1,000  i         i 
1.000            J 
1,000            i 

1 

M\h. 
114 
114 
114 
144 
144 
162 

TYPE:S  641  TO  654 


TYPES  601  TO  614 


Fig.  4-5.— CABLE,   POWER. 

Cable  Reels. 

In  order  to  niaiiiTain  a  complete  history  of  tlie  various  cables,  each  reel  of 
Sijrnal  Corps  cable  bears  a  brass  tag  marked  with  the  letters  "  S.  C."  and 
a  .serial  number,  this  tag  being  attached  to  the  reel  when  the  cable  there«in 
is  accepted  by  the  Signal  Corps  inspector.  The  tag  is  for  the  juirpose  of 
identifying  the  reel  and  also  the  cable  ami  will  be  removed  only  when  the 
reel  is  returned  directly  to  the  manufacturer,  which  shipment  should  not  be 
made  except  under  advice  from  the  Chief  Signal  Officer  of  the  Army. 

The  Chief  Signal  Officer  of  the  Army  will  assign  reel  numbers  at  the  time 
order  for  cable  is  placed.  The  Department  Signal  Officer,  Eastern  Department, 
will  have  charge  of  and  issue  reel  tags.  When  cable  is  manufactureil  in 
!>nother  dei)artnient  and  inspection  is  under  the  direction  of  the  Department 
Signal  Oflicer  of  that  department,  application  will  l)e  made  to  the  r>epartuient 
Signal  Othcer,  Eastern  Department,  who  will  furnish  the  necessary  tags  for 
attachment  to  reels.  Upon  the  placing  of  cable  order,  the  Department  Signal 
Officer,  Eastern  Department,  and  the  department  signal  offi<'er  under  wIio.m' 
direction  inspection  is  to  be  made  will  be  furnished  with  a  copy.     The  latter 

46581°— 17 8  (107) 


8 


Signal  Corps  Manual  No.  3. — Chapter  4. 


will  cause  the  inspector  to  see  that  the  reel  number  and  marking  for  the 
shipment  as  shown  in  the  order  is  followed,  that  the  manufacturer's  name  and 
reel  number  appear  on  the  reel  in  some  permanent  form  (manufacturer's 
name  and  number  will  be  omitted  when  the  reel  becomes  the  property  of  the 
Signal  Corps  by  terms  of  the  order),  and  will  advise  the  Chief  Signal  Othcer 
of  the  Army  of  the  manufacturer's  reel  numbers  corresponding  with  Signal 
Corps  reel  numbers.  If  cable  is  transferred  from  one  reel  to  another,  report 
Avill  be  made  at  once  to  the  Chief  Signal  Officer  of  the  Army  through  the 
Department  Signal  Officer,  showing  the  amount  and  type  of  cable,  the  reel 
from  which  removed,  and  the  reel  on  which  wound.  Cable  should  not  be 
transferred  to  a  reel  known  not  to  be  the  property  of  the  Signal  Corps  if 
it  is  possible  to  avoid  it.  It  is  not  desired  that  full  lengths  of  cable  held  in 
stock  be  transferred  for  the  purpose  of  freeing  manufacturer's  reels,  but  other 
conditions  being  equal,  cable  on  reels  the  property  of  manufacturers  should  be 
used  first. 


^^^^^^^^^■^'flp^^^^^H| 

Fig.  4-6.— REEL,  CABLE,  WITH    LAGGING. 


In  the  installation  of  cal)le  systems  it  is  customary  to  collect  a  quantity  of 
empty  reels  before,  returning  them  to  one  of  the  general  supply  depots  if 
property  of  the  Signal  Corps,  or  the  manufacturer  if  property  of  the  contractor. 
Construction  parties  sIkjuUI  invariably  return  lagging  to  reel  as  soon  as  prac- 
ticable inasnuu'h  as  the  lagging  is  considered  a  part  of  the  reel.  In  former 
years' the  lagging  of  cable  i-eels  was  given  away  or  u.s(>d  as  kindling  for  fire, 
but  the  material  advance  in  the  cost  of  lumber  has  made  such  action  a  waste 
that  is  prohii)ited.  Manufacturers  require  that  the  unbroken  lagging  be  re- 
turned with  reels. 

Installation  of  .(Baulks. 

Submarine  cal)k's  an-  usually  laid  by  the  j)ersoniiel  of  one  of  the  cable 
ships.  The  cable  ships  Un-  laying  and  repairing  harbor  lire-control  cables 
are  each  equipped  with  an  enormous  reel  permanently  installed  in  a  vertical 
position  on  forward  main  deck.  The  revolving  of  this  reel  in  either  direction  is 
accomplished  by  means  of  electric  motors  under  control  of  an  operator  who 
is  stationetl  near  reel.    The  cable  to  be  laid  is  wound  on  reel  described  above, 

(108) 


Cable  and  Cable  Systems. — Chapter  4.  9 

thereby  releasing  reels  upon  wliicli  caliU'  was  sliiiipi'd.  As  the  ship's  reel 
will  hold  many  miles  of  cable,  it  is  probable  that  the  amount  to  be  laid  may 
comprise  that  contained  on  several  shiitpiny  reels.  Before  proceeding  with  the 
actual  laying  it  will  be  necessary,  of  course,  to  splice  the  cable  from  the 
several  shipping  reels.  The  sliore  ends  of  the  calile  are  landed  by  employ- 
ing ship's  launch  and  small  boats.  When  one  end  has  been  landed  and  securely 
fastened  the  ship  proceeds  over  the  route  selected,  the  cable  paying  out  over 
a  large  sheave  at  a  speed  reguhited  by  the  reel  operator.  Continuous  tests 
during  the  laying  of  the  cal)le  are  made  with  delicate  testing  ap|taratus  in 
order  that  a  fault  may  be  detected  as  soon  as  possible.  When  the  lauding  of 
cable  is  completed,  the  ends  are  securely  anchored  by  means  of  chains.  It  is 
more  desirable  that  a  submarine  cable  separate  than  to  have  the  ends  pulled 
out  to  sea.  After  a  cable  is  laid,  a  report,  showing  its  type,  length,  number 
of  splices,  insulation  resistance,  ohmic  resistance,  electnjstatic  capacity,  and 
other  data  is  submitted  by  the  connnanding  otlicer  of  cable  ship  to  the  Chief 
Signal  Odicer  of  the  Army  and  copies  to  others  who  are  authorized  to  receive 
such  reports. 

In  harbors,  to  avoid  as  much  as  possible,  interruptions,  due  to  rupture  of 
cabies  by  ship  anchors,  not  only  have  routes  been  selected  which  will  avoid 
crossing  "  much  used ''  anchorages,  but  a  list  of  forbidden  anchorages  cov- 
ering paths  of  all  submarine  cables  installed  by  the  Signal  Corps  has  been 
prepared  and  furnished  the  Hydrographio  Ofhce  of  the  Navy  Department,  with 
request  that  it  be  embodied  in  "  Notice  to  Mariners  "  issued  by  that  office.  It 
is  believed  that  this  action  will  obviate  to  a  great  degree  interruptions  which 
have  been  occasioned  by  vessels  anchoring  in  the  vicinity  of  cables. 

Signs  reading  "Cable  crossing — don't  anchor"  have  been  installed  at  suitable 
points  near  cable  landings,  and  while  in  some  instances  such  action  has  been 
effective,  in  a  great  many  instances  the  signs  have  apparently  been  ignored. 

Complete  list  of  cable  gear  and  supplies  may  be  found  in  chapter  8  of  this 
manual. 

Aekial   Cahle. 

Soin<>linu's  cables  used  in  post  telephone  systems  are  installed  aerially, 
existing  ixtle  lines  being  employed  as  much  as  possible.  In  the  installaticm  of 
aerial  cable  a  messenger  consisting  of  stranded  galvanized-steel  cable  is 
stretched  tightly  and  fastened  securely  at  each  pole,  care  having  been  pre- 
viously taken  to  guy  the  poles  substantially  where  necessary.  The  cable  is 
then  drawn  along  messenger,  being  suspended  from  it  by  hangers,  one  tyi)e 
of  which  is  made  fast  to  cable,  another  type  being  clamped  to  messenger. 

UNUEUUKorM)    C  VIU.K. 

It  is  desirable  to  jilace  cables  under  ground  wherever  practicable.  This 
avoids  the  pole  lines  and  the  necessity  for  ruiuiing  pole  lines  about  the  post 
in  conspicuous  locations,  secures  the  cable  from  many  sources  of  injury  com- 
mon to  aerial  lines,  and  makes  the  system  reliable  in  operation  and  easy  to 
maintain.  Underground  construction  will,  in  general.  I)e  more  exi)ensive 
than  aerial,  and  this  consideration  will  usually  determine  the  form  of  con- 
struction to  be  followeil.  The  first  step  is  to  decide  on  the  general  layout  of 
the  system.  The  procedure  should,  in  general,  be  the  same  as  outlined  for  the 
aerial  plant.  In  selecting  the  routes,  attention  should  be  given  to  the  contour 
of  the  post;  location  of  material  obstacles  to  cable  runs;  buildings,  existing 
and  projected,  and  probable  extensions  of  the  system  in  the  future.     The  runs 

(100) 


10  Signal  Corps  Manual  No.  3. — Chapter  4. 

between  manholes  .should  be  without  curves  or  bends.  A  diagram  of  pair  dis- 
tribution similar  to  figure  4-7  should  be  made,  after  which  the  lengths  of  the 
various  sizes  of  cable  can  be  determined. 

Two  general  methods  of  placing  cable  under  ground  may  be  followed — trench- 
ing and  conduit.  The  first  costs  less  to  install  and  does  not  require  skilled 
labor,  but  has  the  disadvantage  that  the  cable  is  not  readily  accessible  for 
repair  and  once  installed  can  not  easily  be  recovered.  Trenched  cable  is  also 
more  liable  to  mechanical  injury  after  laying.  It  may  be  stated  as  general 
that  trenching  will  be  confined  to  lateral  runs  of  type  251  cable.  All  paper- 
insulation  cable,  as  far  as  practicable,  will  be  placed  in  conduit. 

DOUBLE  QUARTERS  OmCERS'  QUARTERS  OFFICERS'  QUARTERS 

CQr^JX)    O    Qo.^    QunrJO    Q  0    Q    O    Q    Q 

1^ '  \ ^  -TT  i  Oik:idcdistj-ii>utjnqpoi'fs 

1 3r  armored  cable.  tylK  251  trenched  iiopr-K"  ADMIN.  BUILDING  I   ^  Fused jgrm ma I-.1.       ^1  1 

'^_         __ Al1.^£I'<^ r~%PS<L'j%e^ _  ^^S-^T7nr 

~        ~    Type4Oi.l0poir.J~conduiL     20 paiF.  type,A03~^i^  ^Type.'iOI~o'p7^JfJriaT  "  "'^^ 

P05C  teUnitc/>bai\ 

I' 

I  ill 

4  lO  pair  type  40I  _J|1 '2.!^—^R''-i2L— 

"  '•ji^FuSoJt^-Srpdi.  -pr--jnr^_^^^^^^^/-  lpoirJypeM[m,or,riu,t 


NON-COM.  OFF.  QRTRS.  "Si  .  .     _         ^IFC.Z;.-.... , 


NON-COM.  OFF.  QRTRS.  "^ 

k|  STORL  ^ 

I 


^OUSE.S 

SIS 


5;s 


□  □  I=D — 

PUMP  HOUSE  F.C.SWBD.ROOM  HOSPITAL  FROMjCORAU 

Fig.  4-7.— CABLE   SYSTEM,    DIAGRAMMATIC. 

Tkenching  Cablk. 

The  route  being  staked  out,  the  trench  should  be  excavated  of  sullicient  width 
ai'id  not  less  than  18  inches  in  depth  if  practicable.  Care  should  be  taken  that 
the  bottom  of  the  trench  and  the  first  earth  used  for  filling  in  are  entirely  free 
from  stones,  sticks,  or  other  material  which  will  injure  the  cable  shealli  under 
pre.ssure.  The  cal)le  may  be  pulled  into  the  completed  trencii  from  the  reel, 
held  on  cable  jacks.  lu  pulling  into  trench,  avoid  drawing  cable  over  sharp 
jirojections  which  would  .score  the  shcalli.  ^'hc  same  precautions  should  be 
employed  in  sealing  ends,  splicing,  and  pot-heading  as  for  aerial  cable.  After 
the  cable  is  laid  and  spliced  the  trciicli  may  be  filled.  The  route  of  trench 
with  splices  located  sliould  Ix'  recorded  on  scale  map. 

ro.NDurr. 

Ill  all  coiidiiil  cniistruclidii  llic  roiJowing  geiieral  outline  will  apply: 
The  top  of  the  coiHlnit  line  slionid  never  he  less  than  IS  inelu>s  below  the 
surface.  In  many  places  this  depth  will  be  exceeded  in  order  to  maintain  the 
grade  of  the  duct  line.  The  distance  between  manholes  should  be  as  great  as 
local  conditions  and  the  length  of  the  cable  tiiat  can  be  pulled  into  a  duct 
will  j»ermit.  Where  fibei"  or  pump  log  conduit  are  used  this  distance  should 
not  exceed  4(M)  feet;  for  clay  conduit  8.")()  is  considered  the  niaxinuun.  As 
cable  is  usually  furiiislied  in  lengths  of  1,(MM»  feet,  the  spacing  sliouhl  be  such 
as  to  cut  this  length  without  wa.ste  or  accunndation  of  short  pieces. 

In  general,  it  is  desirable  to  run  conduit  or  trench  in  rear  of  buildings  and 
(piarters  to  avoid  cultiiig  up  tuif  or  lawns  unnecessarily.  The  location  of  the 
main  line  slionhl  he  such  as  to  alToi-il  Ihe  most  e<'onomical  and  convenient  dis- 

(110) 


Cable  and  Cable  Systems. — Chapter  4. 


11 


trilMiti(Hi  to  stations.  All  cxcaviitioiis,  csiM-cially  on  luadsvays,  should  he 
^iianUMl  outside  ol!  w«»rking  liours  by  suitable  barricade  and  lanterns  to  prevent 
injury  to  tralTK-.  Avoid  openin;;  lont;  .stretrlics  of  trench  in  which  the  cable 
or  c<»nduit  can  not  be  laid  without  delay.  In  many  cases  a  plow  nuiy  be  use<l 
to  good  advantage  tct  remove  the  top  layer  of  earth.  Conduit  will  not  be  laid 
in  concrete  unless  four  or  more  ducts  are  used.  Conduit  should  be  laiil  in 
straight  line,  and  at  same  grade  between  maidioles  if  practicable.  All  changes  in 
direction  should  be  made  at  a  nuinliole  <ir  handhole.  The  bottom  of  the  trench 
should  be  smooth  and  firmly  tamped  before  laying  i-onduit.  All  work  in  con- 
nection with  conduit  constructi<in  should  be  accomplished  un<ler  the  suiM»rvisi«m 
of  a  thor(»ughly  competent  foreman. 

The  types  of  conduit  used  are  bituminized  liber,  pump  log,  and  vitrified  clay. 
For  most  of  the  Signal  Corjis  work  the  fiber  conduit  will  be  useil  on  ac<-onnt 
of  ea.se  of  installation  and  small  tirst  co.st  of  material. 

The  vitrified-clay  conduit  is  suitable  for  conditions  riNpiiring  unusual  strength 
and  rigidity.  The  plans  shown  herein  are  for  fiber  <<>ndnit  in  all  ca.se.s.  Where 
this  type  is  not  available  use  may  be  made  of  either  of  the  other  types. 

The  standard  fiber  conduit  is  made  in  5-foot  lengths.  3-incli  inside  diameter 
and  three-eighths  inch  wall,  weighing  2  pounds  per  foot.  The  lengths  of  con- 
duit are  made  with  male  and  female  slip  joints  as  shown  in  figure  4-8.     When 


Fig.  4-8.— CABLE   SYSTEM.   CONDUIT    ENDS. 

laying  the  conduit  the  end  of  each  .section  should  be  dipped  into  a  water- 
proofing liquid  before  jointing.  Care  should  be  taken  t(»  close  the  joint  com- 
pletely and  to  avoid  placing  st<mes  or  other  material  next  the  conduit  in  fillir»g. 
The  work  of  laying  may  be  begun  at  a  manhole  or  at  any  i»art  of  the  trench. 
Where  the  conduit  work  is  disctintlimetl  temporarily  for  any  cause  the  ex- 
posed duct  eiuls  should  be  plugged  and  coveri'd  with  a  tari>aulin  until  work  is 
resumed.  Where  short  lengths  are  niiuired  the  standard  i)ii'ces  may  be  cut 
with  a  handsaw,  using  water  to  jirevent  sticking  of  the  saw.  Care  should  be 
tised  in  handling  the  «"onduit  to  avoid  breaking  the  emls.  The  liber  conduit  is 
made  up  in  the  iisiinl  I'lhiiws.  fi-f^;.  :ind  bends. 

MAMKlI.KS. 

To  provide  for  acce.ss  to  conduit  for  pulling,  splicing.  in.sp«H'tion.  and  repnir 
»)f  cables,  manholes  are  placed  as  needed.  The  usual  form  is  shown  in  figure 
4-9.  The  dimensii>ns  of  this  figure  may  l)e  varitnl  to  suit  s|HH'ial  condition.s.  A 
large  number  of  fornuilae  are  in  use  for  mixing  concrete.  The  proj>ortions  for 
stone,  sand,   an<l  cement  varv   with   th«>  size  and  character  of  the  stone,  the 


(111) 


12 


Signal  Corps  Manual  No.  3. — Chapter  4. 


quality  of  the  cement,  and  the  purpose  for  which  the  con(^rete  is  to  be  used.  A 
good  general  formula  is  1  part  cement,  3  parts  sand,  and  6  parts  stone.  For 
gravel,  1-2J-5  will  be  better.  In  making  estimates  it  should  be  borne  in  mind 
that  the  volumes  of  cement,  gravel,  sand,  and  stone  taken  separately  will  be 


PLAN 


Grouncf  /me 


SECTION 

Fig.  4  9.— CABLE    SYSTEM,    MANHOLE. 

groat<'r  tlian  tlic  voiiinir  of  Die  linislKMl  concrete,  and  aHowance  must  l)e  made 
accordingly.  Thus,  for  1  cuhic  yard  of  concrete  by  the  fornuila  \-'A-C>,  there 
will  be  nece.s.sary  1.1  barrels  of  cement,  0.4G  cubic  yard  sand,  and  0.9.'?  cubic 
yard  st(»ne.    One  barrel  of  cement  coiilaiiis  four  l)ags.    Thi'  formula  is  for  parts 

(112) 


Cable  and  Cable  Systems. — Chapter  4. 


13 


^ i»k' ^ 


jai' 


\         \ 


\         I         I 


/       !     '.----■•- lt----l:----n H vi     ■       \ 

y/c-%H.".-;4--*-----v-^li^-=---i^----v.ii-------i!------:^Xr^^^ 

''.-.-.-..-...-.■^4f^-.-.-.-k.-i^^.-.^yA^      I      ~SN^Or------i^vi------------iK"-- 


SECTION    OF  MANHOLt 
Fig.  4-10.— CABLE  SYSTEM,    MANHOLE  WITH   CONCRETE  TOP. 
(113) 


14 


Signal  Corps  Manual  No.  3. — Chapter  4. 


by  volume.  The  cement  should  be  only  the  best  grade  Portland,  the  sand  free 
from  loam  or  similar  foreign  matter,  the  stone  hard  and  sharp,  screened,  and 
not  larger  than  will  pass  through  a  li-inch  ring.  The  cement  should  be  stored 
only  in  a  perfectly  dry  place.  The  materials  should  be  thoroughly  mixed  before 
adding  water.  Only  such  quantities  should  be  mixed  as  can  be  placed  without 
a  delay  of  more  than  45  minutes.  Water  should  be  added  very  gradually 
and  thoroughly  mixed  with  the  materials  as  applied.  The  materials  should 
be  accurately  measured  and  not  estimated.  Mixing  should  be  done  on  a  board, 
never  on  the  ground.  The  excavation  for  the  manhole  being  completed,  the 
bottom  shall  first  be  laid,  extendding  under  the  manhole  walls.  The  concrete 
shall  be  tamped  in  place  and  the  surfaces  smoothed  off. 

CONCRETE  MANHOLE    FORM 


PLAN  or  FORM   ASSEMBLCO 


BRACt  RODS  B  «  C     . 
DRACe  ROD  A 


Fig.  4-11.— CABLE   SYSTEM,    MANHOLE,    REMOVABLE   FORMS. 

The  form  for  the  walls  should  be  made  of  good  dres.sed  lumber,  substantially 
put  together  to  withstand  the  pr(>ssuro  of  the  concrete.  The  forms  should  bo  so 
built  as  to  be  easily  removed  for  iise  elsewhere.  After  forms  are  set  and  properly 
braced  the  concrete  should  be  placed  to  form  a  wall  of  the  required  thickness. 
In  some  locations  no  outside  form  will  be  required,  the  earth  wall  serving  this 
end.  The  concrete  should  be  deposiled  in  layers  not  more  than  G  inches  thick 
and  rammed  in  place  until  the  surface  becomes  slightly  fluid.  The  manhole 
Khould  be  completed  at  one  operation.    A  surface  for  the  cover  is  made  of  cement 


(IH) 


Cable  and  Cable  Systems. — Chapter  4. 


15 


and  tlio  cover  placed  Ijefore  tlie  cenieiit  lias  set.  In  liiiure  I  t)  liie  cover  is  sliowri 
(j  inches  below  the  surface,  to  allow  for  resoddiiit;.  Where  this  is  not  required 
the  depth  of  the  duct  line  below  the  surface  may  be  reduced  to  place  cover  Hush 
with  ground  line.  In  many  ca.ses  where  it  is  necessary  to  provide  access  to  duct 
for  distribution,  inspection,  etc.,  a  much  smaller  manhole,  usually  terme<l 
"  handhole,"  will  be  sufficient.  This  should  follow  the  general  outline  of  figure 
4-9,  with  an  in:  ide  diameter  of  V2  by  15  and  12  inches  deep,  walls  not  over  0 
inches  thick.  In  many  cases  where  the  handhole  is  used  to  end  a  lateral  to  a 
building  the  foundation  may  form  one  side  of  the  handhole.  The  method  of 
construction  is  the  same  as  for  manholes.  It  is  desirable  t(j  have  (Mily  one  size 
for  all  manholes  and  for  all  handholes,  so  that  one  set  of  forms  will  do  for  each 
type,  ^^'here  concrete  can  not  be  useil,  recourse  may  be  had  to  brick  or,  in 
emergency,  creosoted  plank  not  less  than  2  inches  thick.  In  some  instances  it  is 
advisable  to  furnish  a  cover  equipped  with  a  throat  in  order  that  entrance  to 
manhole  will  be  liush  with  earth's  surface,  and  in  other  instances  a  more  expen- 
sive construction  such  as  is  shown  in  figure  4-10  may  be  desired.  The  latter  has 
a  cast-iron  cover  of  somewhat  dilTerent  design  adapted  t(j  withstand  heavy  traf- 
fic. The  dimensions  of  manhole  given  in  this  figure  are  not  to  be  taken  as  stand- 
ard. The  type  to  be  adopted  depends  on  the  number  of  ducts,  local  contours, 
location,  etc.  In  figure  4-11  is  shown  a  set  of  removable  forms  for  constructing 
concrete  manholes  of  this  character.  Where  a  number  are  to  be  constructed  of 
one  size  it  will  be  found  desirable  to  use  this  or  a  similar  set  of  forms.  These 
should  be  made  by  local  labor  and  of  serviceable  lumber. 


MAN HOLE  I 

Fig.  4-12.— CABLE   SYSTEM,    DISTRIBUTION. 


The  method  to  be  used  in  branching  from  a  main-line  conduit  to  a  building 
or  group  of  buildings  retiuires  careful  thought.  Where  the  lateral  is  (»f  sulhcient 
length  and  the  number  of  pairs  requires  a  paper-insulation  cable,  a  branch  line 
of  duct  with  a  handhole,  as  shown  in  figure  4-12,  should  be  used.  The  handhole 
is  located  at  the  wall  of  the  central  structure  of  the  group,  and  the  cable  ends 
in  a  can  terminal,  as  shown.  From  the  can  terminal  single-pair  cables  are 
brought  down  to  the  handholes  and  are  then  run  to  each  of  the  buihlings.  being 
trenched  only  after  leaving  the  handhole.  The  height  of  the  can  terminal  above 
the  ground  is  not  fixed,  but  usually  should  be  about  ii  fivt.  In  some  cases  the 
terminals  may  be  placed  in  basements,  umler  porches,  inside  storehouses,  etc., 
where  the  installation  can  be  simplified.  Connection  from  unilerground  to 
aerial  cable  may  be  made  as  shown  in  figure  4-13. 


(115) 


16 


Signal  Corps  Manual  No.  3. — Chapter  4. 


ft^jl<.T|l';\>^  .-.Ml>->=il"...<!>^,     1,11,  _ 


o 

z 

zo 

8^ 


(110) 


Cable  and  Cable  Systems. — Chapter  4. 

PULLIN«   CABLE   IN    CONDUITS. 


17 


L'uder  no  circuiiistaiHvs  .should  a  cal)!!-  .splice  he  ihiIIlmI  in  cundiiil. 

Tlio  conduit  system  hcin^'  (■(►nipjctcd,  |>r.t'iiaiation  (or  itullinji;  in  cajjle  is  made 
by  tin-cadinj:  a  rop*'  tlu'ou^'li  the  »hi<ts.  Tins  may  he  acconii)iislH'd  l)y  tir.st  pusli- 
ing  tlirougli  duct  rods  of  sections  3  or  4  feet  iu  length,  with  coupling  devices 
on  each  end,  or  u  steel  wire,  known  as  u  "  tish  wire"  or  "snake."  (U.se  may 
be  made  of  wooden  strips,  approximately  i  by  1  inch,  cro.ss  .section,  notched  at 
the  ends  and  spliced  together  with  iron  wire  or  by  means  of  taping,  the  two 
ends  to  be  taped  .separately  and  again  wrai)ping  the  ends  with  tape,  after  the 
two  have  b«'en  placi-d  together.) 

The  pulling-in  roi>e  is  now  attached  to  one  end  of  the  length  of  win*  or  rods 
in  the  duct  and  pulled  in.  The  cable  reel  is  pla<«'d  near  manhole  on  jacks,  as 
shown  in  figure  4-14. 

One  or  more  men  tend  the  reel  and  see  that  the  cable  feeds  off  freely.  A  man 
In  the  manhole  directs  the  cable  into  the  duct  and  prevents  injury  to  .sheath 
from  pulling  across  sharp  corners.  The  pulling-in  rope  may  be  attached  to  cable 
by  a  manufactured  device  shown  at  bottom  of  figure  4-l."5,  or  by  an  improvi.setl 
one  shown  at  top  of  same  figure,  which  is  made  as  follows : 


Fig.  4-14. -CABLE    PULLING.  POSITION    OF   REEL. 

Place  n  block  of  wood  about  H  iiulies  wide  against  tlie  end  of  the  cable;  cut 
G-foot  'engths  of  number  10  or  12  B.  \V.  G.  steel  wire;  take  two,  thrtn*,  or  four 
of  these  wires,  depending  on  the  severity  of  the  pull,  and  bunch  them  together, 
bend  them  in  the  middle  on  the  block  of  wood,  then  wrap  the  two  halves 
spirally  around  the  cable  sheath  in  opposite  directions,  twisting  the  ends  se- 
curely together.  When  the  pull  of  the  rope  comes  on  these  wires,  they  biutl 
harder  on  each  other,  on  the  lead,  the  insulation,  and  tlie  conductors,  as  the 
pull  grows  luirder.  The  seal  on  the  lead  of  the  cable  is  not  broken,  and  n<i 
water  can  come  in  contact  with  the  insulation. 

In  pulling  in  paper-insulation  cable  of  large  size  where  tlie  strain  is  unusually 
great,  it  is  advisable  to  make  pulling  roi)e  fast  to  all  conductors,  as  well  as 
sheath,  in  manner  just  described.  This  method  is  objiMtionable,  liowever.  es- 
pecially if  tliere  be  nuid  or  water  in  ducts,  and  is  only  resorted  to  iiy  the  Signal 
Corps  when  there  is  tlanger  of  stretching  lead  sheath  of  cable  to  a  dangerous 
degree. 

(117) 


18 


Signal  Corps  Manual  No.  3. — Chapter  4. 


Manila  rope  is  usod  for  drawini::  cable  tlioii^ili  stoel  rope  may  ho  used.  The 
ends  of  the  rope  should  be  fitted  with  an  eye  around  a  steel  thimble  fastened 
to  a  short  length  of  chain  with  a  swivel.  The  swivel  may  have  a  pair  of 
sister  hooks,  all  as  shown  in  figure  4-15. 


Fig.  4-15.— CABLE   GRIPS,    IMPROVISED   AND    MANUFACTURED. 

If  the  cable  is  small  and  run  short,  it  may  be  pulled  in  by  hand.  For  heavy 
cables,  winches,  windlass,  or  horsepower  may  be  used.  The  rope  should  be 
led  from  the  duct  to  surface  over  pulleys  when  the  depth  of  the  manhole  makes 
a  direct  pull  inadvisable.  Two  pulleys  on  shafts  which  can  be  inserted  in 
any  of  a  number  of  holes  in  two  channels  are  used  for  this  purpose,  the  lower 
pulley  being  placed  opposite  the  duct  and  the  upper  at  a  height  sufficient  to 
carry  the  rope  out  of  the  manhole.  Enough  slack  cable  should  be  left  in  each 
manhole  for  splicing  and  placing  the  cables  along  the  sides,  leaving  the  center 
clear.  After  drawing  in,  examine  all  ends  carefully  to  see  that  the  seal  is  in- 
tact. Two  or  even  three  cables  of  the  sizes  commonly  used  in  Signal  Corps  work 
may  be  pulled  into  one  duct  if  drawn  together.  I'uUing  in  a  second  cable  wilh 
one  already  installed  should  he  avoided  if  practicable. 


HORIZONTAL  SECTION  Of  MANHOU  ^  „„    _^, 

ANO  PLAN  OF  CA8Lt3  '^^    3u^^  *'^°  BRACHtT 

Fig.  4-16.— CABLE    RACKING    IN    MANHOLES. 

When  distance  b»'tw<M'n  manholes  is  not  over  200  feet  cable  may  be  pulled 
through  one  manhole  and  on  to  next,  provided  the  pull  is  in  a  continuous 
straight  line.  The  advisability  of  doing  this  is  strictly  u  matter  of  judgment 
on  the  r>art  of  person  in  charge  of  cable  pulling  and  .slunild  be  regulated  by  the 
amount  of  extra  strain  on  cable  <'aused  by  such  action.  When  a  cable  is 
pulled  tlirough  one  manhole  and  on  to  the  next,  slack  should  be  i)ulled  back  in 


(118) 


Cable  and  Cable  Systems. — Chapter  4.  1.9 

tlie  intermediate  nianholc  in  order  tiial  ^■n\>h'  may  lie  racJicd  on  .sides,  thereby 
i<eei)in};  center  of  ail  manlioles  clear. 

A  zinc  tag  on  which  is  stamped  the  designation  number  is  attached  to  each 
cable  in  each  manhole  by  means  of  galvanized-iron  wire.  In  manholes  where 
cable  is  to  be  spliced,  the  tag  described  above  should  be  placed  on  each  .of  the 
two  ends  to  be  spliced  together  in  order  that  splicer  will  not  make  a  mistake. 

As  soon  as  cable  has  been  pulled  in  ducts  the  Signal  Corps  representative 
supervising  cable  pulling  must  complete  a  preliminary  record  which  has  been 
I)repared  on  the  ground  prior  to  initiation  of  cable  pulling  and  upon  which  has 
been  recorded  designation  number,  type,  and  pair  size  of  each  cable  of  the 
system  and  the  number  of  the  duct  to  be  used  in  each  stretch  for  each  cable. 
The  following  is  also  recorded:  Pulled  length  of  cable,  reel  number  from  which 
cable  was  taken,  and  date  pulled.  The  name  of  splicer  and  the  date  of  making 
each  splice  is  entered  on  this  record  after  splicing  is  initiated. 

The  arrangement  of  cables  in  manholes  should  be  carefully  planned  to  avoid 
sharp  bentls,  have  all  cables  accessible  for  inspection  and  repair,  and  keep  the 
center  free  for  future  operations.  The  cables  shouUl  be  supported  on  the  side 
walls  by  hangers  or  supports  of  a  type  similar  to  tho.se  shown  in  tigure  4-16. 
This  tigure  shows  the  ideal  arrangement  for  a  large  number  of  cables.  Where 
only  one  or  two  cables  are  in  place  tlu\v  may  be  supported  by  means  of  pipe 
straps  attached  to  wall  with  screws  and  exi)ansion  anchors. 

Cable  Splicing. 

The  splicing  of  cable  is  an  operation  which  should  be  undertaken  only  by 
an  experienced  man.  In  the  installation  of  cable  systems  there  should  be  em- 
ployed for  splicing  the  subterranean  cables  one  or  more  cable  splicers  who  have 
previously  shown  that  their  work  is  satisfactory.  If  it  becomes  nece.ssary  to 
employ  one  who  is  not  known,  his  work  should  be  closely  scrutinized  by  person 
in  charge  of  the  installation  until  satistied  that  he  is  competent. 

The  importance  of  the  above  will  be  realized  when  the  fact  is  considered  that 
cables  of  any  great  length  must  necessarily  contain  a  number  of  splices,  and 
that  a  splice  poorly  made  may  not  only  make  "test  after  laying"  (which  will 
be  described  later)  indicate 'that  the  cable  is  faulty,  but  may  render  the  circuits 
contained  in  the  cable  inoperative  if  repairs  are  not  made. 

When  laying  submarine  cable  the  splicing  is  invariably  acconiplislied  liy  the 
personnel  of  the  cable  ship.  These  men  have  bad  a  wlile  expi-rience  in  this 
branch  of  work  and  are  experts  in  their  line. 

The  Signal  Corps  issues  a  chest  containing  all  necessary  tools  for  the  work 
of  si)li(ing  cables,  the  contents  of  which  are  enumerated  in  chajUer  S  of  this 
manual. 

Where  an  emergency  splice  must  be  made,  the  following  directii>ns  should  be 
followed  : 

SPLICING    RIBBEU    INSl  LATION     SIUMAKINK    CAULE. 

Materials  required  : 

Pure  rubber.  Tape,  okonite. 

Rubber  cement.  Tape,  friction. 

Serving  mallet  (can  be  improvised).  Tape,  P.  &  B. 

Small  .soldering  kit.  Small  coil  .11  mils  galvanized  iron  wire 
Spun  yarn  for  seizing.  (seizing). 

Sandpaper.  Vulcanizer  (if  vulcanized  splice). 

Alcohol.  00  iier  cent  compound  (if  vulcanized 
Splicing  compound  splice). 

(119) 


20  Signal  Corps  Manual  No.  3.— Chapter  4. 

(d)  Cut  the  ends  of  the  cable  to  be  spliced  squarely  off  and  have  one  overlap 
the  other  about  15  feet. 

(b)  The  armor  wires  are  then  carefully  untwisted  from  one  of  the  ends  for 
aboixt  15  feet  in  groups  of  about  five.  These  should  be  carefully  handled  so 
they  will  go  back  into  place  easily  (fig.  4-17). 

(c)  Before  unlaying  armor  wires  some  small  galvanized  wire,  called  "seiz- 
ing," is  wound  tightly  around  the  cable  here  to  prevent  the  untwisting  from 
going  any  farther  back. 

(d)  The  jute  padding  is  then  untwisted  and  the  core  is  cut  off  to  within  a 
foot  of  the  small  wire  seizing,  and  the  jute,  about  2  feet  from  it.  Meantime  a 
seizing  of  small  wire  is  wound  aboiit  6  inches  from  the  other  end  of  the  cable. 

(e)  The  armor  wires  are  nicked  with  a  tile  and  broken  off  close  to  the  latter 
seizing. 

(/)  The  armor  wires  are  then  smoothed  with  a  file. 

(g)   The  jute  is  stripped  off  the  short  end. 

(h)   The  tape  is  taken  off  for  6  inches  at  each  end. 

(0  The  rubber  insulation  is  cut  in  cone  shape  with  a  sharp  knife  (lig.  4-17). 
leaving  about  3  inches  of  conductor  exposed  at  each  end.  The  copper-conductor 
strands  are  spread  out  for  li  inches,  the  central  wire  being  cut  out  of  each 
for  that  length. 

(;■)  The  wires  are  well  cleaned  with  fine  sandpaper  and  the  ends  are  inter- 
laced and  neatly  and  closely  wound  about  the  twisted  parts  of  each  other. 

(/r)  The  joints  should  be  soldered  at  the  ends  of  the  copper  strands  only, 
using  a  very  little  resin  as  a  flux.  Care  must  be  taken  to  prevent  the  resin 
from  touching  the  clean  rubber  surfaces.  Acid  soldering  flux  of  any  kind 
must  positively  not  be  used. 

A  well-vulcanized  insulatiou  for  the  joint  is  always  desirable,  but  proper 
vulcanizing  requires  almost  laboratory  conditions  and  considerable  extra  time, 
and  where  a  cable  is  being  spliced  on  shipboard  with  ship  pitching  in  rough 
water,  time  may  be  a  vital  factor.  In  view  of  this,  there  has  been  developed 
by  the  Signal  Corps  a  method  of  iusulating  submarine  cable  joints  without 
vulcanizing,  which  has  proved  highly  satisfactory.  The  joint  produced  by  this 
method  is  termed  a  "raw  joint"  and  has  been  used  willi  marked  success 
for  over  live  years  by  personnel  of  the  U.  S.  Army  transport  Jiiirnsidc.  The 
cable  ends  are  prepared  and  the  two  ends  of  conductor  joined  as  described 
al)ove.    Continued  description  is  as  follows : 

III  jireparing  the  conductor  of  each  cable  before  joining  same,  allow  at 
least  2  inches  of  the  core  to  be  exposed  from  where  it  comes  out  of  the 
jute  to  the  end  of  the  cone  or  "pencil  point"  of  the  rubber  insulation.  One 
inch  of  this  will  be  taken  up  in  forming  the  cone  shape,  the  other  inch  of 
exposed  core  retaining  its  original  cylindrical  shape. 

liefore  proceeding  further  it  is  w(>ll  to  note  that  u])ini  tlH>  ih'kikm-  care 
in  i)reparing  tliese  2  inclu^s  of  core  at  either  side  of  lh(>  jitiiit,  may  depiMid 
the  success  or  failure  of  tlH>  insulating  (pialities  of  the  finished  splice. 

In  shaping  lh(;  cone,  wiiicli  is  done  with  a  sharp  knife,  the  core  is  grasped 
in  the  left  hand  and  iMillcd  taut;  at  the  place  where  the  cone  is  to  terminate 
nick  the  surfiicc  ni'  ilic  nililicr  fur  a  marker,  placing  the  forefinger  of  the 
left  hand  for  su])iiort  under  that  part  of  the  core  where  tiie  cone  is  about 
to  b(»  shaped,  <-(»nnnence  making  the  cut,  <lrawing  the  blade  of  the  knife 
toward  the  hand  holding  the  core,  giving  the  blade  a  sawing  movement, 
which  will  assist  greatly  in  the  cutting,  particularly  if  the  rubber  is  soft 
anil  fresh.     Do  not  try  to  make  s[)eed  or  save  labor  by  fornung  the  cone  in 


(120) 


Cable  and  Cable  Systems. — Chapter  4. 


21 


(121) 


22  Signal  Corps  Manual  No.  3.— Chapter  4. 

only  four  or  five  cuts.  After  the  coue  has  been  shaped  with  the  knife  as  well 
as  possible,  care  having  been  taken  at  all  times  not  to  nick  the  copper  con- 
ductor, a  piece  of  rough  sandpaper,  about  No.  2,  is  then  used  to  round  up 
the  cone,  removing  all  flat  places  and  ridges,  this  sandpapering  also  con- 
tinuing vigorously  and  thoroughly  over  that  portion  of  the  core  which  re- 
tains its  cylindrical  shape.  Any  flat  places  or  ridges  not  removed  from  this 
part  of  the  core  will  have  a  tendency  to  form  grooves  along  the  core  under 
insulating  material  which  will  cover  it,  allowing  moisture  to  woi*k  its  way 
in  to  the  conductor. 

If  the  cylindrical  part  of  the  core  is  not  thoroughly  cleaned  and  roughened 
by  the  sandpapering,  that  adhesion  which  is  necessary  between  core  and  insu- 
lating material  wrapped  on  will  not  take  place. 

The  conductors  having  been  joined  and  the  ends  soldered,  the  rubber  core 
and  conductor  over  which  the  insulation  is  to  be  wrapped  should  be  washed 
Avith  alcohol  on  a  piece  of  clean  cloth  or  waste  to  remove  any  oil,  dirt,  or  mois- 
ture that  may  have  been  deposited  on  them  due  to  handling. 

Allow  adhering  alcohol  to  evaporate.  If  necessary,  then  scrape  the  rubber 
with  the  edge  of  knife  blade,  to  remove  any  lint  or  threads  that  may  have  been 
left  on  the  rubber  after  washing  with  alcohol. 

The  joint  is  now  ready  for  the  insulating  materials  to  be  wrapped  on. 

The  part  of  joint  most  susceptible  to  leakage  is  where  the  insulating  material 
and  rubber  core  join.  A  good  grade  of  rubber  cement,  such  as  is  used  for  patch- 
ing the  inner  tubes  of  automobile  tires,  should  then  be  put  on  the  rubber  core 
and  rubbed  into  the  pores  of  the  rubber,  which  has  been  roughened  and  scraped 
for  this  purpose.  When  this  first  coating,  which  has  been  put  on  rather  thin, 
has  dried — which  it  will  do  almost  innnediately— a  second  coating  should  bo 
applied,  and  if  necessary  a  third,  the  object  being  to  form  a  thin  coating  or 
sleeve  around  the  core,  which  becomes  a  part  of  the  core  itself.  As  this  last 
coMting  becomes  sticky  (as  it  does  just  before  drying),  a  piece  of  pure  ruber  tape 
about  3  or  4  inches  in  length  is  wrapped  on,  commencing  about  a  quarter  of  an 
inch  from  the  point  of  the  cone,  across  the  bare  conductor,  and  running  up  to  the 
other  cone  for  about  a  quarter  of  an  inch ;  the  wrapping  is  then  continued 
back  to  the  starting  point,  each  turn  overlapping  the  previous  one.  Now,  hold- 
ing the  unused  end  of  the  rubber  tape  with  one  hand,  cover  the  freshly  wTapped 
rubber  with  a  thin  coating  of  cement,  distributing  it  eveidy  and  quickly, 
then  wrap  on  another  layer  of  pure  rubber.  Apply  a  thin  coating  of  cement 
over  this  also.  Next  wrap  on  the  splicing  compound,  conunencing  at  the  large 
end  of  the  cone,  wrai)ping  over  tlu«  pure  rubl)er  and  up  to  the  large  end  of  the 
other  cone,  then  back  again,  continuing  till  the  joint  has  been  built  up  slightly 
larger  than  the  original  core.  No  cement  is  used  between  or  over  tlie  layers 
of  splicing  compound. 

Again  ai)i)ly  the  cement  to  Uiat  i)art  of  the  core  as  y(4,  unwrapped,  and 
when  ready,  wraj)  onto  the  core  two  layers  of  okonite  rubbi'r  tape,  which  will 
bring  that  part  of  the  core  to  the  same  diameter  as  the  joint  ;  continue  the  third 
layer  of  okointe  all  the  way  across  the  Joint,  build  up  the  core  on  that  side, 
then  continue  ba<-l<  across  the  joint  to  the  starting  jioint.  Touching  a  warm 
iron  to  the  end  of  tlie  okonite  will  kee])  it  from  unwrapping  when  you  let  go 
of  it. 

Now  wrajt  one  layer  of  Iriclioii  tape  over  the  joint  Ironi  cml  to  end.  allow- 
ing the  tape  to  overlaf)  about  half  its  width  each  turn,  this  wrapjting  to  be  put 
on  as  tight  as  possible,  to  act  as  a  compress  and  binder  for  the  rubber  over 
which  it  is  laid. 

(122) 


Cable  and  Cable  Systems. — Chapter  4.  23 

Over  all  of  this  wrap  two  layers  of  I*.  &  I!.  tai>e,  commencing  at  one  end  of 
the  joint ;  wrap  completely  across,  and  then  back  again  to  the  starting  point, 
occasionally  warming  the  tape  with  a  torch,  if  necessary,  to  make  it  lay  on 
close  and  even. 

The  joint  is  now  ready  to  be  warmed  up.  Ai)ply  the  flame  of  the  gasoline 
torch  directly  to  the  P.  &  B.  tape,  moving  the  tlame  back  and  forth  along  the 
top,  bottom,  and  sides  of  the  joint  until  the  insulating  compound  in  the 
P.  &  B.  tape  is  melted  and  commences  to  drip.  Then,  for  convenience  in  han- 
dling while  laying  on  armor  wires,  wraj)  on  one  layer  of  friction  tape  with 
just  enough  tension  to  make  it  lay  on  evenly.  The  joint  is  now  ready  for  the 
armor  wires  to  be  laid  on. 

Note. — The  compound  of  the  P.  &  B.  tajie,  which  is  in  itself  an  insulator, 
will,  when  melted  as  above,  give  sufficient  heat  to  cause  the  okonite  tape  to 
form  a  rubber  sleeve  over  the  joint.  The  friction  tape  between  the  okonite 
and  P.  &  B.  serves  the  purposes  of  a  form  or  compress,  holding  the  okonite, 
which  has  been  wrapped  on  with  some  tension,  and  preventing  its  opening  up, 
due  to  its  own  tension,  if  tlie  lieat  should  not  be  evenly  applied  to  all  points 
simultaneously.  The  pure  rubber  next  to  the  copper  conductor,  which  is  pri- 
marily put  on  for  the  purpose  of  preventing  possible  deterioration  of  the  cop- 
per by  the  rubber  compounds,  will,  when  put  on  as  in  the  above  joint,  serve  as 
an  extra  precaution  against  leakage. 

(I)  The  armor  wires  are  then  returned  to  place,  which  they  will  easily  do 
if  care  has  been  taken  in  handling  them.  It  will  be  observed  that  over  1.5  feet 
of  the  armor  from  one  side  will  lap  over  that  end  from  which  the  armor  was  not 
removed. 

(m)  The  armor  replaced,  the  wires  are  then  bound  in  place  with  several 
seizings  of  small  galvanized-iron  wire  tightly  and  evenly  wrapped. 

(h)  The  entire  splice  should  then  be  served  with  a  closely  wound  layer  of 
spun  yarn.  The  proper  way  of  doing  this  is  with  the  serving  mallet.  (See 
fig.  4-17).  (^f  course,  if  means  are  not  present  to  do  it  <jtherwise,  it  shoulti  be 
served  by  hand. 

(o)  After  splicing,  the  bight  should  be  carefully  lowered  by  small  ropes 
attached  to  each  side  of  it  to  prevent  straining  or  jerking  the  splice. 

THK   VULCANIZED    .JOINT. 

As  previously  stated,  a  well-vulcanized  insulation  for  a  joint  is  always 
desirable  and  should  be  made  as  follows:  The  preparation  of  the  cable  ends, 
the  joining  of  copper  conductor,  the  coning  of  insulation,  the  application  of 
first  layer  of  pure  rubber  tape,  and  the  replacing  and  serving  of  armor  wires 
should  be  accomplished  identically  as  just  described  for  the  "  raw  joint." 
consequently  only  the  remaining  insulating  of  conductor  splice  will  be  described 
in  the  following  remarks. 

A  60  iier  cent  rubber  compound  in  the  form  of  tape  is  wrapped  closely, 
smoothly,  and  evenly  over  the  pure  rubber  previously  placeil.  the  edges  of  the 
former  overlapping  each  other,  until  the  joint  has  been  built  up  to  a  slightly 
larger  diameter  than  the  mold  in  which  it  is  to  be  compressed  and  heated. 
Great  care  should  be  exercised  in  all  wrapping  to  preclude  the  possibility  <»f 
air  pockets  forming  beneath  the  layers.  Before  being  placed  in  the  vulcanizer. 
a  piece  of  paper  should  be  folded  and  laid  over  the  joint  to  prevent  com- 
pound sticking  to  mold.  After  the  vulcanization  has  been  completed  and 
the  joint  removed  from  mold  the  edges  of  paper  may  be  trimmed  with  shears 
and  then  imusteneil  and  scrubbed  off  so  joint  can  be  insi)ecte».l  for  flaws.     In 

46581°— 17 9  (123) 


24  Signal  Corps  Manual  No.  3. — Chapter  4. 


all  vulcanizing  of  joints  the  compounds  placed  as  just  stated  are  subjected 
to  compression  and  heated  to  an  even  temperature  approximating  220°  F. 
lor  approximately  40  minutes. 

There  are  various  ways  of  accomplishing  the  above.  It  is  believed  that 
electric  vulcanizers  which  have  been  used  by  the  Signal  Corps  on  the  U.  S. 
Army  transport  Biiniskle  are  the  most  satisfactory  apparatus  for  this  work 
where  a  source  of  electric  current  is  available.  They  are  a  specially  con- 
structed heater  equipped  with  proper  resistance  for  maintaining  required 
temperature  for  a  given  voltage.  The  heater  consists  of  two  pjirts  so  arranged 
that  when  the  upper  is  clamped  to  lower  a  groove  in  upper  half  comes  directly 
over  groove  in  lower  half  forming  a  concentric  aperture  somewhat  larger 
than  the  diameter  of  the  cable  core  and  several  inches  in  length.  In  between 
these  two  electrically  heated  plates  is  placed  the  joint  to  be  vulcanized,  the 
upper  plate  being  forced  down  toward  the  low^er  plate  by  means  of  a  hand 
screw,  which  keeps  the  joint  under  pressure  during  the  time  of  vulcanization. 

Where  it  is  not  practicable  to  use  the  electric  vulcanizer,  such  as  for  portable 
work,  remote  from  a  source  of  supply  of  electric  current,  and  it  is  desired  to 
make  the  joint  as  with  the  electric  vulcanizer,  the  same  results  can  be  obtained 
by  the  use  of  two  iron  blocks  each  about  2  inches  square  and  6  or  8  inches 
in  length  with  a  semicircular  groove  in  one  side  of  each  block  extending  the 
full  length,  and  the  blocks  so  arranged  by  means  of  dowel  pins,  or  preferal)ly 
a  shoulder  running  the  full  length  of  both  sides  of  the  lower  block,  to  assure 
the  alignment  of  one  groove  over  the  other  when  the  two  blocks  are  placed 
together.  In  the  top  of  the  upper  block  a  hole  is  bored  of  sufficient  size  and 
depth  to  permit  of  the  insertion  of  the  bulb  of  a  thermometer  for  the  i)ur- 
])ose  of  observing  the  temperature  of  the  blocks.  A  couple  of  ordinary  iron 
hand  clamps  are  then  used  to  press  the  upper  and  lower  blocks  together  on 
the  joint  to  be  vulcanized,  and  heat  applied  with  a  gasoline  torch.  By  watch- 
ing thermometer  closely  any  desired  temperature  can  be  maintained,  as  the 
mass  of  the  iron  blocks  is  sufficient  to  prevent  sudden  variations  of  the 
temperature. 

"When  the  electric  vulcanizer  or  the  iron  l)]ocks  previously  doscrilied  are  not 
available  the  joint  can  be  vulcanized  by  using  hot  ])arafhn,  as  follows:  After 
having  completed  the  wrapping  of  the  rubber  compound,  wrap  on  over  this 
as  tightly  as  i)ossible  two  layers  of  friction  tape  lo  act  as  a  binder  or  compress, 
extending  this  wrapper  of  friction  tape  well  back  on  llie  original  rubber  <-()re 
so  that  any  part  of  the  original  rubber  core  Hint  ni;iy  also  be  in  Ihe  i)Mra(rni 
during  the  time  of  vulcanization  will  not  be  exposed.  If  this  precaution 
is  not  taken  the  rubber  core  itself  may  be  injured.  In  addition  to  the  friction 
tape  it  js  a<lvisable  to  wrap  twine  lightly  over  the  outside  of  the  joint  at  the 
ends  where  the  new  rubber  compound  is  wrai)ped  onto  the  cone  shapes  of 
the  original  rubber  core,  as  it  is  at  these  points  most  dillicult  to  secin-e  that 
cohesion  which  is  necessary  for  a  water-tight  joint.  After  the  joint  has  been 
vulcanized  and  cooled  this  twine  may  be  cut  and  taken  olT. 

The  paraffin  is  heated  by  placing  the  tray  in  which  it  is  contained  over  the 
flames  (tf  a  gasoline  furnace,  and  when  brought  up  to  the  proper  temperature, 
which  is  determined  by  means  of  a  thermometer  immersed  in  the  paraffin,  the 
joint  is  then  placed  in  the  paraffin  and  allowed  to  renuiin  the  required  length  of 
time.  Fr«'(iu('nt  readings  of  the  thermometer  are  made  during  the  time  of 
immersion  of  the  joint  in  order  to  maintain  an  even  heat.  The  temperature 
readings  should  be  taken  <-los('  to  ihe.  joint,  as  under  certain  conditions  there 
may  be  a  wide  range  of  different  temperatures  in  tlie  same  tray. 

(124) 


Cable  and  Cable  Systems. — Chapter  4.  25 

AN'lioro  tlu>  00  piT  fi'Ut  cuuipuuud  and  the  tiim,'  lor  ahovo  is  not  avnihililf,  a 
puxl  water-tifTlit  j»»iiit  can  be  made  by  usinj,'  tbe  i)ure  or  "  Para  "  rubber  entirely. 
Tins  rublRU-  cut  into  strips  of  about  tbree-fourths  intli  widtli  sliould  lie  tlior- 
oujibly  warmed  and  wrapped  on  closely  and  smootldy  l»ut  not  too  tijriitiy.  If 
the  I'ara  is  wrapi)ed  on  cold  and  stretched  ti;:htly  it  may  he  found  that  when 
the  joint  is  remove<l  from  the  heater,  the  conductor,  instead  of  bein;r  in  tiie 
center,  has  been  forced  to  one  side ;  and  althou^di  from  outward  appearances 
the  joint  may  appear  perfect  there  may  be  no  more  than  a  thin  tiim  of  ruhi)er 
covering;  one  side  of  the  conductor.  Tiiis  jiossiide  condition  is  eliminated  by 
thoroughly  warming  the  rubber  before  wrai»ping  on,  as  the  rubber  will  then 
pull  in  two  before  the  tension  with  which  it  is  wrapped  on  becomes  great 
enough  to  cause  the  condition  of  nonconcentricity  as  shown  above. 

The  electric  vulcanizers  wliich  have  been  furnisheil  the  Biirnside  in  making 
joints  t)f  this  kind  give  a  temperature  of  220°  F.,  and  allowing  the  pure  or 
Tara  rubber  joint  to  remain  in  these  heaters  for  15  to  20  minutes  at  that  heat 
lias  been  found  sutlicient  time  to  give  a  good  water-tight  joint. 

In  all  of  the  above  methods  it  will  be  noticed  that  a  considerable  length  of 
time  and  preparation  is  required  for  the  heating  process  alone,  in  addition  to 
\\  hicli  there  is  the  time  required  for  the  preparation  of  the  jijint  before  heating, 
as  also  the  replacing  of  the  armor  wires,  putting  on  the  seizing  wires,  and 
serving  over  the  whole  splice  with  spun  yarn. 

On  the  cable  ship  this  element  of  time  is  a  large  factor  in  deti'miiiiing  the 
kind  of  joint  to  be  made;  especially  so  has  this  been  the  case  on  the  Biinisidc 
during  the  last  several  years,  most  of  the  work  being  in  Alaskan  waters  during 
the  winter  months,  under  the  most  unfavorable  weather  conditions,  when  the 
successful  accomplishment  of  repairs  being  made  may  depend  upon  the  expe- 
diency with  which  the  various  operations  pertaining  to  the  repairs  are  per- 
formed. 

SPLICING    PAPKK-INSULATION    SUBMARINE    CABIJ*:. 

The  armori'i!  portion  of  the  cable  is  treated  as  described  for  rubber  insu- 
lation submarine  cable,  except  that  extra  precaution  should  he  taken  in  covering 
the  lead  sleeve  of  splice,  especially  where  outside  diameter  of  sleeve  reduces  to 
outside  diameter  of  cable  sheath.  It  may  be  necessary  to  till  in  between  armor 
wires  of  cable  with  extra  lengths  of  armor  wire,  due  to  enlarged  diameter  over 
sleeve,  before  serving  completed  splice  with  spun  yarn. 

The  details  of  the  splice  otherwise  conform  to  description  for  the  si)licing  of 
all  paper-insulation  cables  appearing  later  under  this  subject. 

This  tyi>e  of  cable  is  fre(iuently  used  in  underground  construction  where 
trenching  is  re-sorted  to.  With  such  use  an  alternative  method  of  protecting 
the  splice  is  to  cover  it  with  a  3  or  4  foot  length  of  iron  pipe,  it  being 
necessary  to  slip  pipe  over  one  end  of  cable  before  splicing  is  started.  When  this 
method  is  employed,  the  piiie  .should  be  left  in  a  position  slightly  off  the  horizon- 
tal, in  order  that  water  will  not  be  apt  to  stan«l  in  pipe.  With  a  well-made  joint 
the  only  objection  to  water  in  pipe  is  the  likelihood  of  it  freezing. 

SPLICING  OF  ALL  PAPER-INSULATION   CABLES. 

Material  required. — The  following  inattMi.il   will  he  i-etpiired  ftir  each  splice: 
(ff)   Paper  sleeve.s,   or   their   approved   e((uivalent,   for   covering   the   joint   in 
each  conductor. 

(6)   Paraffin  for  drying  the  splice. 

(125) 


26 


Signal  Corps  Manual  No.  3. — Chapter  4. 


(c)   Strips  of  nuislin,  or  its  approvod  ocp.iivalont,  fur  wrapping  tlie  splice. 

((f)   Lead  sleeves. 

(e)   Solder  for  seams  and  wiped  joints. 

(/)  Gummed  paper  for  limiting  the  wiped  joints. 

Before  being  used  the  paper  sleeves  should  be  immersed  in  liot  i)aralhn,  or 
otherwise  thoroughly  dried,  until  they  are  entirely  free  from  moisture. 

For  wrapping  the  core  after  splicing  and  for  binding  the  ends  of  a  splice, 
strips  of  muslin,  or  its  approved  equivalent,  should  be  used. 

Sleeves  should  be  made  of  the  same  material  of  which  tlie  cabh'  sheaths  arc 
made  or  of  pure  lead. 

The  thickness  of  the  lead  sleeve  covering  the  si)lice  shall  be  one-eighth  of  an 
inch  when  the  inside  diameter  of  the  sleeve  is  3  inches  or  less,  and  three-six- 
teenths of  an  inch  when  the  inside  diameter  of  the  sleeve  is  more  than  3  inches. 

The  dimensions  of  sleeves  which  may  be  used  in  splicing  cables  of  various 
sizes  are  given  in  the  following  tables.  Where  the  cables  to  be  spliced  together 
are  not  of  the  same  size,  the  proper  sleeve  for  the  largest  of  the  cables  shall 
be  used. 

Jjcad  .s'/cercs-  for  f<trciifilit  s/iUcc-s. 


No.  19  gauge  wire. 

No.  22  gauge  wire. 

Niiinl)er 
of  pairs. 

Inside 
diameter. 

Lengtli. 

Inside 
diameter. 

Length. 

15 
20 
25 
30 
50 
75 
100 

ir,o 

ISO 
200 
300 
400 

Inches. 
1 

n 
1^ 

2 

2 

2\ 

3 

3 

3i 

3* 

4 

Inches. 
16 
16 
16 
16 
16 
16 
16 
18 
18 
18 
22 

Inches. 
1 
1 

1'. 
1'. 
2 
21 

2i 

2.\ 
3" 
3i 
3§ 

Itiches. 
16 
16 
16 
16 
16 
16 
16 
16 
16 
18 
18 
22 

1 

Lead  sleeves  for  3-way  or  "  Y  "  spUccs. 


No.  19  giiage  wire. 

No.  22  gauge  wire. 

Number 
of  pairs. 

Inside 
diameter. 

Length. 

Inside 
diameter. 

Length. 

10 
20 
25 
30 
50 
75 
100 
l.W 

180 
200 
300 
400 

Inches. 
1 

ij 

2 

2i 
3 
3i 

4 
4i 

4i 

Incites. 
16 
16 
16 
16 
16 
16 
18 
18 
18 
22 
22 

Inches. 

1 

1.', 

1'. 

2 

2.'. 

3 

3i 

4 

4 

4 

4.', 

4i 

Indies. 
16 
16 
16 
16 
16 
16 
18 
18 
18 
18 
22 
22 

i 

For  splicing  cables  with  larger  conductors  than  arc  given  in  the  tables, 
sleeves  may  be  used  of  which  tiie  h-ngtii  is  al)out  dgbl  times  the  outside 
diameter  of  tlie  cable  and  of  which  the  inside  diameter  is  alxMil  .10  i)er  ctMit 
greater  tlian  the  outside  diameter  of  the  cable. 

(126) 


Cable  and  Cable  Systems.— Chapter  4. 


So  far  as  possililc,  splices  >IhiuI(1  Ik-  liiiislictl  .-ukI  sdldcri-tl  till'  (lay  tiny  aiv 
begun.  Where  necessary,  if  the  surroundings  he  dry,  an  nntinislied  splice  may 
l)e  left  open  overnight  provided  it  l)e  carefully  wrapped  and  jirotected  rniiii 
moisture  Ity  a  rul)i)er  blanket  or  other  suitable  covering.  In  wet  or  daniii 
surroundings,  however,  work  on  a  splice  should  i)e  continuous  until  tinishetl. 
In  such  cases  the  splice  shonld  be  "boiled  out"  with  paraflin  at  interval."* — 
say.  after  eacii  .10  ])airs  have  been  coiuiected. 


Fig.  4-18.— CABLE.    PAPER    INSULATION.    SPLICING. 

Whenever  it  may  be  necessary  to  leave  the  cable  end  it  should  he  thoroughly 
dried  and  sealed  with  solder,  as  much  care  being  taken  as  if  the  joint  were 
to  be  permanent. 

If  it  is  suspected  that  moisture  has  entered  the  end  of  a  cable,  a  short  length 
of  it  should  be  cut  off  and  dipped  into  hot  paraflin.  when  the  presence  of 
m(»isture  will  be  indicated  by  a  characteristic  frying  sound.  If  there  is  len.L'th 
to  spare,  the  cable  should  be  cut  back,  a  short  portion  at  a  time,  until  it  gives 
no  eviilence  of  dampness. 

After  this  the  end  should  be  thorouglily  drieil  with  paratlin  and  a  splice 
made  or  the  end  sealed,  as  already  described. 

The  operations  of  making  a  straight  splice  in  their  sequence  are  as  follows : 

1.  After  being  sure  that  no  moisture  exists  in  either  of  the  cable  ends  to 
be  spliced,  remove  the  lead  sheath  from  eai-h  end  for  a  distance  equal  to  the 
length  of  the  lead  sleeve  used. 


^^5/ 


/> 


^ 


m 


2 


r 


Fig.  4-19.— CABLE,    PAPER   INSULATION,   SPLICING. 

In  removing  the  sheath  care  must   be  taken   not  to   injure  the   insulation 
of  the  wires.     (Figs.  4-lS  and  4-11).) 

(127) 


28 


Signal  Corps  Manual  No.  3. — Chapter  4. 


2.  The  core  is  tightly  bound  witli  strips  of  muslin,  or  its  approved  equivfl- 

lent,  at  the  end  of  the  cable  sheath,  patking  the  binding  close  to  the  sheath. 

This  is  done  to  prevent  the  wires  from  being  cut  on  the  edge  of  the  sheath. 
(Fig.  4-20.) 


Muslin 


Fig.  4-20.— CABLE,    PAPER    INSULATION,    SPLICING. 

3.  In  general,  as  soon  as  possible  after  the  removal  of  the  lead  sheath  the 
exposed  conductors  are  thoroughly  "  boiled  out "  by  pouring  hot  paraffin  over 
them  until  all  traces  of  moisture  are  removed.  The  binding  must  be  saturated 
with  paraffin  as  well  as  the  core.  Enough  paraffin  remains  in  the  core  to  form 
a  seal,  which  protects  the  cable  against  moisture  while  the  splice  is  being 
made.  The  temperature  of  the  parattin  should  be  above  that  of  boiling  water, 
but  must  not  be  high  enough  to  scorch  or  make  brittle  the  paper  insulation. 

In  drying  or  '•  boiling  out  "  a  splice  with  paraffin,  always  work  away  from  the 
cable  sheath  toward  the  end  of  the  conductors  or  middle  of  the  splice  in  order 
to  prevent  any  moisture  being  driven  under  the  sheath.  The  paraffin  should  be 
poured  on  with  a  ladle.  The  paraffin  draining  off  may  be  caught  in  the  melting 
pot  or  a  pan 


Fig.  4-21.— CABLE,    PAPER    INSULATION,    SPLICING. 
(128) 


Cable  and  Cable  Systems. — Chapter  4. 


29 


4.  The  ciuls  of  tlu-  lahlf  slicatlis  ami  <<(  tin-  lead  sleev»*  sliouhl  1)0  scraiied 
l)riKht  fur  3  or  4  inches  and  rubbetl  wiili  lallow,  or  its  approved  eipiivaleiit,  to 
Iveep  them  clean  during  tlie  suljsequeut  work  on  tlie  splice.  The  tallow  also  acts 
as  a  llux  in  niakinj,'  the  wiped  joints. 

5.  The  lead  sleeve  is  next  slipiied  over  the  end  of  one  cable  and  moved  hack 
out  of  the  way. 

0.  The  two  cables  are  placed  an«l  lirinly  secured  in  the  same  straight  line, 
with  the  distance  between  the  ends  of  the  sheaths  alntut  3  inches  less  than  the 
length  of  the  lead  sleeve. 


Fig.  4-22.— CABLE,    PAPER    INSULATION,    SPLICING 

7.  After  the  cables  are  in  position  the  conductors  are  bent  out  of  the  way  and 
shall  then  be  spliced  in  the  following  manner: 

8.  Starting  at  the  center  or  the  lower  back  side  of  the  cables,  a  pair  of  wires 
from  each  cable  is  loosely  brought  together  with  a  partial  twist  (a,  fig.  4-21), 
thus  marking  by  the  bend  in  the  pairs  the  point  at  which  the  j(»int  is  to  be  made. 
Slip  a  paper  sleeve  over  each  wire  of  one  pair  and  push  the  sleeves  back  far 
enough  to  allow  room  for  making  the  joint. 


Fig.  4-23.— CABLE.    PAPER    INSULATION,    SPLICING. 
(1291 


30 


Signal  Corps  Manual  No.  3. — Chapter  4. 


The  wires  are  now  to  be  connected  by  a  splicer's  ordinary  twist  joint  {h, 
fig.  4-21).  The  like  wires  from  the  two  pairs  to  be  spliced  are  brought  to- 
gether at  the  point  marked  by  the  bend  and  given  two  or  three  twists  (c, 
fig.  4-21).  Remove  the  insulation  of  both  wires  beyond  the  twist,  being  care- 
ful not  to  nick  or  scrape  the  conductors.     The  wires  are  now  to  be  bent  as 


Fig.  4-24.— CABLE,    PAPER    INSULATION,    SPLICING. 

shown  and  twisted  together  as  if  turning  a  crank.  This  action  insures  good 
contact  even  though  the  wire  may  be  coated  with  a  film  of  paraffin  due  to 
the  "  boiling  out "  process.  The  ends  are  cut  off,  so  as  to  leave  the  twist  of 
bare  wire  not  less  than  1  inch  in  length.  The  twist  is  bent  down  along  the 
insulated  wire  and  the  paper  sleeve  slipped  over  the  joint  {d,  fig.  4-21).  The 
completed  joint,  with  the  sleeves  in  place,  is  shown  in  e,  figure  4-21. 


Fig.  4-25.— CABLE,    PAPER    INSULATION,    SPLICING. 

For  conductors  of  large  size  (No.  13  B.  &  S.  gauge  or  larger)  the  wires  may 
be  joined  by  means  of  a  Western  Union  Telegraph  joint  or  other  approved 
method.     Tlic  joint  is  covered  with  a  paju'r  sleeve. 


Fig.  4-26.— CABLE,    PAPER   INSULATION,   SPLICING. 
(130j 


Cable  and  Cable  Systems. — Chapter  4. 


31 


III  spliciiifT.  catv  shoiihl  \>v  liiki-ii  to  sjiliie  ilic  ceiilcr  ami  lower  pairs  tirst, 
foriiiiiiK  tlie  outer  pairs  about  tJie  (viili'r  pairs  so  tliat  the  tiuishetl  splice  may 
liave  a   uniform  shape. 

In  piekiufr  out  the  pairs  to  be  .sidjced  lo^ieljier  care  sliouhl  be  taken  to  trans- 
pose the  circuits  thoroughly.  It  is  sullicient  if  the  transposin;;  lie  done  between 
pairs  in  tlie  correspond injr  layers  of  the  two  cables. 

The  wire  joints  should  be  distributed  alonjx  the  whole  len;,'lli  of  the  splice 
in  order  to  keep  the  .spliie  uniform  in  size  and  shape. 

9.  When  all  the  wire  joints  have  been  ma<le,  the  splice  is  afrain  "boiled  <iut  " 
with  hot  parallin  until  all  traces  of  moisture  have  been  removeil.  In  apiilylufi 
this  parallin,  work  from  the  ends  of  the  si»lice  toward  the  middle. 

10.  The  splice  is  then  wrajiped  with  strips  of  muslin,  or  its  approved  ecpiiva- 
lent,  and  compressed  until  the  lead  sleeve  will  just  sliji  over  the  splice.  Tare 
mu.st  be  taken  not  to  compress  the  splice  too  tijrhlly  or  tin'  wires  may  be  forced 
through  the  insulation  and  .ro^.w  in  the  splice  result. 


Fig.  4-27  —CABLE.    PAPER    INSULATION.   SPLICING. 

The  splice  is  dried  out  with  hot  paralbn  after  the  tirst  wrapping  of  muslin 
has  been  put  on  and  apain  after  the  wrapping.'  of  the  .splice  is  complete.  The 
dryiuff  out  is  continued  until  bubbles  cease  to  appear  on  the  splice. 

11.  The  lead  sleeve  is  slipped  into  place  before  the  splice  has  had  time  to 
cool,  taking  care,  however,  to  see  that  the  sleeve  is  perfectly  dry. 

The  ends  of  the  sleeve,  which  should  overlap  the  cable  sheath  at  each  end  by 
about  1*  inches,  are  beaten  down  to  conform  to  the  cable  sheath  and  a  wipe<l 
joint  carefully  nuide  at  each  end.  In  making  the  wiped  jtiints  strips  of  gumuKtl 
paper  may  be  used  to  limit  the  joints. 

Wiped  joints  should  be  carefidly  inspected,  using  a  mirror  when  necessary 
to  detect  any  imperfections  in  the  .'jeal. 


TllKKK-WAV     OK     "Y         SIM. ICES. 

The  method  of  making  a  thret^-way  or  Y  splice  Is  the  same  as  for  a  straight 
splice  except  in  the  following  particvdars: 
There  are  two  general  tlas.ses  of  Y  splices — 

1.  Whea-e  the  cables  all  end  at  the  splii-e. 

2.  Where  a  branch  cable  is  to  be  spliced  into  a  contiiuious  cable. 

In  the  tirst  case  the  method  is  generally  similar  to  a  straight  sj)lice.  The 
sheaths  of  all  three  cables  are  removeil  for  a  length  equal  to  the  length  of  the 
lead  sleeve.  The  two  cables  forming  the  main  cable  are  secin-t»«l  in  n  straight 
line  with  the  distance  between  the  ends  of  the  sheaths  about  3  inches  less  than 
the  length  of  the  sleeve.  The  bran<-h  cable  is  la.she«l  beside  one  •)f  the  main 
cables  with  the  end  of  its  sheath  opitosite  the  end  of  the  sheath  of  the  mulu 
cable. 


32  Signal  Corps  Manual  No.  3. — Chapter  4. 

The  joint  is  made  by  twisting  together  lilce  wires  of  pairs  from  each  of  the 
three  cables,  taking  care  to  include  two  or  tliree  twists  of  the  insulation  in  the 
joint  in  the  manner  hereinbefore  described  for  straight  splicing. 

The  lead  sleeve  in  this  case  may  be  a  whole  sleeve.  It  should  be  slii^ped  on 
and  pushed  back  on  that  portion  of  the  main  cable  away  from  the  branch. 

In  the  second  case  a  split  lead  sleeve  must  be  used. 

The  sheath  of  the  main  cable  shall  be  removed  for  a  length  of  about  3  inches 
less  than  the  length  of  the  sleeve.  The  sheath  shall  be  removed  from  the  end 
of  the  branch  cable  for  an  equal  distance. 

The  branch  cable  is  lashed  to  the  main  cable,  with  the  end  of  the  sheath 
opposite  the  end  of  the  sheath  of  the  cable. 

A  pair  of  conductors  in  the  main  cable  is  cut.  To  one  end  of  each  conductor 
is  spliced  a  short  piece  of  bare  wire  of  the  same  size  as  the  cable  conductors. 
This  wire  should  be  twisted  into  the  insulation  two  or  three  times,  in  order  to 
prevent  its  pulling  back  on  the  conductors.  The  second  end  of  the  main  con- 
ductor, the  free  end  of  the  bare  wire,  and  a  like  conductor  of  a  pair  in  the 
branch  cable  are  twisted  together,  in  the  manner  already  described,  and  covered 
with  a  paper  sleeve  which  is  long  enough  to  cover  both  ends  of  the  bare  wire. 

If  there  is  slack  enough  in  the  main  cable,  the  joint  may  be  made  without 
splicing  in  the  bare  wires. 

In  putting  on  a  split  lead  sleeve  the  seam  must  be  carefully  soldexed,  then  the 
ends  beaten  down  to  conform  to  the  sheaths  of  the  cables  and  soldered  with 
wiped  joints  at  each  end.  Care  should  be  taken  to  retouch  the  ends  of  the 
seam  after  the  wiping  is  complete,  in  order  to  make  sure  that  the  seam  has  not 
been  opened  while  the  wiping  was  in  progress. 

A  grooved  wooden  block  should  be  placed  in  the  fork  of  each  Y  splice,  in 
order  to  keep  the  cables  apart.  This  block  is  kept  in  place  and  the  cables  at 
the  same  time  protected  from  the  iiossibility  of  too  great  a  separation  by 
means  of  a  wrapping  of  wire  soldered  to  the  cable  sheaths. 

POT   HKADS. 

It  will  readily  be, seen  that  it  is  impracticable  to  connect  to  terminals,  con- 
ductors of  a  cable  wrapped  with  manila  paper.  Where  it  is  desired  to  termi- 
nate such  a  cable,  a  rubber-covered  wire  is  spliced  to  each  conductor.  A  lead 
sleeve  fastened  to  lead  sheath  of  cable  by  means  of  "wiped  joint"  is  used  to 
house  such  si)lices  and  also  as  a  container  for  an  insulating  moisture  repellant 
compound,  which  is  jiourcd  as  hereinaffcr  desci'ibed. 

MKTHOl)  OK   MAKING   A   VOT   HKAl). 

This  description  covers  the  method  of  making  a  llexible  cable  terminal  or  pot 
hea<l  for  terminating  the  conductors  of  a  lead-incased,  dry-core,  ))aper-insulation 
cable,  with  rui)l»er-covered  conductors,  and  at  the  same  time  effectually  sealing 
the  lead-incased  cal)le  against  the  ingress  of  air  and  moisturt>. 

The  lead  sleeve  or  pipe  of  this  terminal  slumld  have  a  lengtli  of  eight  times  the 
outside  diameter  of  the  cat)le  to  which  it  is  to  be  attaclicd,  jilus  10  inches,  and 
an  outside  diameter  of  at  least  one  and  one-linlf  times  the  outside  diameter  of 
llie  lead  ("liiic.  Tlie  l(>ad  sleeve  sliouhi  linve  a  tlii<'l<ness  not  les-s  than  that  of 
the  shealli  <■  '  tlie  lead  cable. 

The  wires  of  this  terminal,  which  are  to  be  sj>liced  to  those  in  the  lead  cable, 
slutuld  be  covered  willi  okonit(>  insulation  or  its  aj)prov(Hl  ecpiivalent.  The 
MililMi-covcii'd  wires  niav  be  loose  or  in  tlie  form  of  a  tai)ed  cable,  and  should 
be  of  the  size  and  length  retpiired.  .The  Signal  (.'orps  sui)plies  a  rubber-insu- 

(132) 


Cable  and  Cable  Systems.  -Chapter  4.  33 

latldii  twlstt'd  pair  wire,  kiKnvii  as  iMit-hcad  wiiv,  lor  tlu'  [>iiriM»si'  when  loose 
wires  are  eiiiiiloyed. 

All  tape  used  in  the  terminal  should  he  adlicsivi'  or  ruhher  tape  of  tiie  best 
quality. 

The  paper  or  cotton  sleeves  u.sed  should  he  of  the  ordinai-y  form  for  eovering 
wire  joints  in  paper-lnsidation  cahle. 

The  tuhe  for  addinj;  the  compound  to  the  terminal  should  have  an  inside 
diameter  of  one-half  inch  and  a  h-nirth  2  inclu-s  less  than  that  of  the  It-ad 
sleeve.  The  tube  shouhl  have  thin  walls  and  may  lie  made  of  metal,  vul- 
canized llher,  or  manila  paper  i-olled  alVmt  a  half-im-li  i-od  and  hound  thcicin 
with  striufi. 

"While  the  use  of  this  tuhe  is  desirable  it  is  not  necessary  if  ^'reat  care  is 
taki'ii  to  have  the  compound  reach  bottom  of  sleeve. 

The  sole  leather  should  be  ajiproximately  three-sixteenths  of  an  inch  in  thick- 
ness, 3  inches  in  width,  and  lonj;  enoufih  to  wrap  once  about  the  tajied  cable 
or  rubber-covered  wires. 

Heavy  cotton  twine  or  wicking  should  be  used  for  bindin;;  purpt»ses. 

The  wiping  solder  used  should  be  the  commercial  plumber's  wiping  .solder, 
which  is  composed  of  60  per  cent  lead  and  40  per  cent  tin.  It  is  sometimes 
advisable  to  add  a  slight  amount  of  half  and  half  solder  (.")0  per  cent  lead  and 
50  per  cent  tin)  to  slightly  increase  the  proportion  of  tin.  The  latter  is  decided 
by  the  action  of  the  alloy. 

The  sealing  compound  should  be  of  any  approved  waterproof,  semielastic, 
insulating  material,  which,  when  melted,  will  How  readily  into  the  lead  sleeve 
and  about  the  wires  and  adhere  tenaciously  to  the  wires  and  lead  sleeve.  The 
compound  should  not  be  sufficiently  affected  by  the  conditions  of  exposure  as 
to  endanger  the  seal. 

No.  1  ozite  is  the  compound  most  commonly  used. 

DIRECTIONS   1  OK   SKITINC    Tl'   THK   I'OT    HKAO. 
[See  fii.'.  4-2S.1 

No  paraffin  shall  be  used  in  "lioiling  out""  cable  ends  and  sleeves  for  pot 
heads. 

The  proper  amount  of  sheath  should  be  removed  from  the  lead  cable,  the 
lead  sleeve  slipped  over  the  cable,  and  the  cable  wires  .spliced  to  the  rubber- 
covered  wires  in  the  usual  manner,  using  paper  or  cotton  sleeving. 

In  doing  this  work  care  must  be  taken  to  remove  all  i>ieces  of  jiaper,  jute, 
tape,  or  other  things  which  might  obstruct  the  tlow  of  the  compound,  which  is 
to  be  poured  in  after  the  lead  sleeve  is  in  place. 

Close  to  the  end  of  the  lead  cable  sheath  the  paper-insulat«'tl  wires  should 
be  tightly  wound  with  a  number  of  layers  of  twine  or  wicking  in  such  a  maimer 
as  to  prevent  the  compound  from  entering  the  cable. 

If  rubber-insulation  cable  is  u.sed  for  extending  the  coiuUutors  of  paju-r- 
insulation  cable,  the  preceding  remarks  are  applicable  and  the  outer  braid  or 
covering  t>f  the  rubber  cable  should  be  removed  in  order  that  the  <"onductors 
may  separate.  About  lA  inches  of  the  cable,  with  braided  or  other  covering, 
should  enter  the  sleeve. 

At  that  point  on  the  rubber-covered  wires  or  rubber-insulation  cable  which 
will  come  immediately  at  the  end  of  the  lead  sleeve  should  be  wrajiptMl.  lirsi.  a 
single  layer  of  sole  leather,  and  over  this  several  layers  of  adhesive  or  rubber 
tape.  The  leather  should  enter  the  finished  spli«v  about  IJ  inehes  and  i>roje<'t 
the  same  distance. 

(l.">r>) 


34 


Signal  Corps  Manual  No.  3.— Chapter  4. 


Rubber  cabfe  or  nines 


Rubber  rape 
Leather  collar 


Fig.  4-28.-CABLE,    PAPER    INSULATION,   CONSTRUCTION    OF    POT  HEAD. 

(134) 


Cable  and  Cable  Systems. — Chapter  4.  35 

Tlu'  eiitiio  splire  shoulil  next  lie  opened  np  as  nnu-li  as  possible  in  onler  that 
the  sealing  compound  may  flow  readily  iihout  every  wire.  If  a  hemp  ford  he 
found  in  the  rubber  cable  it  should  be  cut  olT  as  close  as  possible  to  the  cable<l 
portion. 

The  one-half  incli  tube  should  then  be  laid  alonj:  in  the  splice  with  one  end 
on  a  line  with  the  end  of  the  lead  cable  sheath  and  fastened  in  position  with 
several  turns  of  twine.  This  twine  .serves  the  double  purjxtse  of  keei)in}r  tlie 
tul)e  in  place  and  reducing  the  splice  to  a  diameter  which  will  allow  the  lead 
sleeve  to  be  drawn  on  without  <listurbin!j;  the  sleeves  C(»vering  the  spliced  wires. 
The  turns  of  twine  should  not  extend  beyond  the  last  of  the  wire  joints  on  the 
ruiiber-covered  wire  end  of  the  s|)lice.  It  should  not  be  drawn  too  tij:htly  but 
should  allow  the  comitound  a  chance  to  t'ft  to  the  wire.  If  the  nianila-paper 
tube  is  used,  the  rod  on  which  it  is  rolled  should  be  ri'tained  in  the  tube  until 
the  splice  is  ready  to  be  tilled. 

The  lead  sleeve  should  be  drawn  over  the  splice,  allowint:  it  to  jirnjt^ct  over 
the  lead  cable  sheath  li  inches,  and  then  connected  to  the  lead  cable  sheath  by 
means  of  a  "wiped"  joint. 

The  lead  cable  sheath,  with  sleeve  attached,  should  now  be  fastened  in  an 
uprijiht  position,  the  sleeve  warmed  until  it  becomes  barely  possible  to  touch 
it  with  the  hand,  and  the  sealing  compound  heated  t<»  as  hijrh  a  temperature  as 
is  possible  without  burning  the  insulation  from  the  wires,  slowly  and  cautiously 
poured  in  through  the  tube,  using  a  funnel  to  assist  in  the  operation.  The 
comi>ound  should  fill  the  sleeve  to  within  one-half  inch  of  the  top.  When  the 
compound  cools  sufficiently,  more  should  be  poured  in  at  the  top  of  the  sleeve, 
the  tube  not  being  used. 

After  the  splice  has  become  thoroughly  cold  the  open  _end  of  the  lead  sleeve 
shoulil  be  carefully  dressed  into  contact  with  the  taped  leather  which  surrounds 
the  rubber-covered  wires  or  cable. 

If  possible  the  pot  head  should  be  mounted  in  an  upright  position.  When 
it  is  necessary  in  insitle  construction  to  place  the  pot  head  in  a  horizontal 
position,  the  open  end  of  the  lead  sheath  should  be  wrapped  with  tape  to 
prevent  the  compound  from  running  out,  and  care  should  be  taken  to  locate 
the  pot  head  where  it  will  not  be  exposed  to  excessive  heat. 

Uubber-lnsulation  lead-sheath  cal)les  are  sometimes  furnished  with  pot 
head  where  they  terminate  in  a  subterranean  cable  terminal  box  or  other 
apparatus  not  supplied  with  a  means  of  sealing  the  cable. 

The  placing  of  pot  head  on  this  type  of  cable  is  a  comparatively  simple 
operation,  pot  head  being  merely  for  the  purpose  of  sealing  the  cable  to  pre- 
vent moisture  entering  it.  A  short  lead  sleeve  is  placed  as  described  under 
pot  heads  for  paper-insulation  cable,  the  condu<'tors  of  cable  extending  beyond 
sleeve  sufficient  distance  to  permit  of  being  laced  into  forms  and  connet>te<l 
to  terminal  strips.  The  sleeve  is  then  filled  with  a  suitable  sealing  compound. 
When  the  compound  cools,  it  will  be  lu'cessary  to  again  fill  the  pot  head,  as  all 
compounds  shrink  perceptibly  upon  cooling. 

SUGGESTIONS    I.N    RliGAItB    TO    SPLICKS. 

In  branching  a  small  lead-covered  cable  from  a  flexible  .splice  or  pot  head 
it  is  considered  advantageous  to  run  it  out  at  the  base  of  the  lead  sleeve, 
making  a  double-wiped  joint,  rather  than  to  run  it  out  with  the  rubber-covere<l 
wires  or  taped  cable.  . 

Should  occasion  arise  when  it  becomes  imperative  to  shorten  the  length  of 
the  leatl  sleeve,  a  sleeve  of  a  greater  diameter  than  is  ordinarily  recommended 
should  be  selected  and  the  space  occupied  by  the  joints  in  the  wires  con- 

(135) 


36  Signal  Corps  Manual  No,  3. — Chapter  4. 

tracted.  keeping  the  .space  between  the  last  wire  joint  on  tlie  rubber-covered 
wire  end  and  the  leather  wrapping  the  same  as  it  would  be  in  a  regular  splice, 
this  being  the  space  where  the  efficiency  of  the  seal  is  maintained. 

The  sealing  compound  should  rise  at  least  one-half  inch  above  the  top  of 
the  paper  tube. 

SPLICING  RUBBEK-IXSULATIOX  LEAD-COVKKEl)   SU15TEKKANEAN   CABLE. 
(Types  213  to  210,  inchislvc.) 
Materials  and  tools  required  are: 


Solder,  resin  core. 
Solder,  wiping. 
Lead  sleeves. 
Cable  splicers  chest. 


Pure  rubber. 
Rubber  cement. 
Adhesive  tape. 
Gasoline. 
Sandpaper. 

The  subterranean  splice  should  be  made  as  follows: 

{a)   Slip  the  lead  sleeve  over  one  end  of  the  cable. 

(6)  Conductors  must  be  thoroughly  cleaned  without  the  use  of  acid  soldering 
flux. 

(c)  The  insulation  must  be  trimmed  cone  shaped  down  to  the  conductor. 
Fan  out  strands,  interlace  them,  and  make  a  Western  Union  joint  (see  fig. 
4-17).     The  central  conductor  may  be  removed  if  the  joint  is  large. 

(d)  The  very  slightest  touch  of  resin  flux  should  be  used.  Use  very  little 
solder.    Do  not  allow  resin  to  touch  rubber  surfaces.     Keep  the  rubber  clean. 

(c)  File  off  all  projecting  points  of  solder  on  conductor. 

if)  Wrap  the  joint  after  treating  with  rubber  cement  with  pui'e  Para  sheet 
rubber  cut  in  strips  one-half  inch  in  width  and  wind,  overlapping  spirally. 
Continue  winding  back  and  forth  until  a  little  beyond  each  of  the  coned  ends 
and  until  the  thickness  of  the  joint  slightly  exceeds  the  original  insulation. 
Rub  a  clean,  warm  iron  toool  over  the  joint  until  the  rubber  fuses  slightly. 
Wrap  a  double  thickness  of  adhesive  tape.  Rub  warm  tool  over  the  finished 
joint,  taking  care  not  to  overheat. 

(fir)  In  splicing  multiple-conductor  cable,  joints  in  pairs  should  be  slightly 
staggered. 

The  lead  sleeve  is  then  i)lace<l  in  position  and  a  "  wijied  "  joint  carefully  made 
at  each  end.  In  making  the  wii)ed  joints,  strips  of  gunmied  paper  may  be  used 
to  limit  the  joint. 

SPLICING  OF  UUnHER-KNSULATlON   LEAO-COVEKKl)  AND  AliMOKKI)  SUBTKKRANEAN   CABLE. 

(Types  217  .Mnd  21S.f 

Material  i-cijuircd  llie  sanu>  as  tiiat  iireviously  (>nuni('rat«Ml  lor  splicing  rubber- 
insulation  lead-covered  subterranean  cable,  and  in  addition  a  ball  of  marline 
and  small  coil  of  .ll  mils  diameter  galvani zed-iron  wire. 

(rt)   ('ut  t»ne  cable  at  the  point  where  the  si)lice  is  to  be  located. 

(b)  The  other  cable  should  overlap  the  first  by  about  8  feet. 

(c)  W^rap  the  shorter  cable  tightly  with  .soft  iron  wire  at  a  point  about  18 
inches  from  its  end. 

(d)  Remove  the  armor  from  the  end  of  the  shorter  cable  with  a  hacksaw 
and  unwind  the  jut<'. 

(e)  Cut  off  lead  armor  at  a  ]»oint  about  10  inches  from  the  (muI. 

(/)  Wrap  the  longer  cal)Ie  tightly  with  soft  iron  wire  at  a  i)oint  18  inches 
back  of  where  splice  will  (tccur.        • 

(g)  ('ut  away  the  jute  and  unwrap  the  armoi-  wire  back  to  the  point  where 
the  cable  has  been  wrappe<l. 

(h)   Slip  on  the  lead  sleeve. 


Cable  and  Cable  Systems. — Chapter  4. 


37 


(/■)    PnK'ood  with  .joint  as  (k'sci-ihcij  uiidcr  IciKl-covfn'd  calilc. 

(j)   Serve  layer  of  jute  or  marline  over  joint. 

(/r)  Serve  armor  wire  over  joint  and  onto  liu>  slmri  t-Mlilc  ;ind  wrap  uitli 
bare  soft  iron  wire  at  its  end. 

(/)   Serve  layer  of  marline  over  the  outside  of  rephui-d  arnioi-. 

When  these  splices  are  made  in  manholes,  the  armor  does  lot  neeil  to  be 
served  over  the  joint.     For  permanent  trenehe<l  cable  this  should  be  done. 

As  an  alternative  the  joint  may  be  covered  with  a  3  or  4  foot  lenjrth  of  irou 
pipe,  it  beiuf?  necessary  to  slij)  i)ipe  over  one  end  of  cable  before  the  si)licini.c  is 
started.  When  this  method  is  employed,  the  pipe  should  be  left  in  a  position 
slifihtly  off  the  horizontal  in  order  that  water  will  not  be  apt  to  stand  in  ]»ipe. 
With  a  well-made  joint  the  only  objection  to  water  standing  in  pipe  is  the  likeli- 
hood of  it   freezing. 


K 

3f—— 

^ 

%^ 

-i-     -^         .,■ 

_J) 

i 
1 

1 

Drill  tliae  holes  \'diom 

1 

G' 

o 

o 

Scale  Pull  size 


Sleeve  and  gland  of  cast  site/ 
Cover  of  mild  rolled  steel 


COVER 


SIDL 


EIND 


SELCTION  THROUGH  SPLICE 
5ptKe-  to  be  soldered  a/xi  ir^sulatrd  nith  rubber  and  fncLon  tape  m  the  usual  marrrer 
•with  fncL'on  iapa  ccrer  for  all  arid  box  ft'lfcd  iritfi  hot  corr^pound 

Fig.  4-29.— CABLE,  TYPE    251,   SPLICING    SLEEVE. 


In  splicing  Signal  Corps  type  251  cable  the  usual  lead  sleeve  may  be  used, 
but  it  is.  impracticable  to  make  a  wiped  joint,  due  to  small  diameter  and  thin- 
ness of  the  lead  sheath  of  this  cable,  consetiut'iitly  the  conductors  should  be 
spliced  and  taped  as  previously  described  for  conductors  of  rubber  insulation 
cable  and  the  lead  sleeve  formed  to  bind  the  armor  of  the  cable  at  either  end. 
By  means  of  holes  through  side  of  sleeve  near  each  end  the  sleeve  is  then 
filled  with  melted  Chatterton  compound  and  the  holes  sealed  tightly  by  means 
of  solder  applied  with  a  soldering  iron. 

Another  methoil  of  splicing  this  type  of  cable  makes  use  of  a  manufacturetl 
splicing  sleeve  designed  for  this  purpost-.     It  is  shown  in  ligure  4-20  and  is 

(137) 


38  Signal  Corps  Manual  No.  3. — Chapter  4. 

there  described  iu  detail  to  such  au  extent  that  further  description  would  be 
superfluous. 

TESTS    OF    SUBTERKANEAN    CABLES   AFTER   THEY    HAVE   BEEN    PULLED    IN    DUCTS    AND 

SPLICED. 

Practically  all  cable  purchased  by  the  Signal  Corps  is  inspected  during  manu- 
facture by  an  experienced  inspector  detailed  for  that  work  exclusively.  The 
duty  of  this  inspector  is  to  watch  closely  the  various  operations  at  the  factory 
and  to  make  all  prescribed  tests  of  material  mentioned  in  the  specification. 
He  should  do  all  in  his  power  to  facilitate  the  manufacture,  but  his  paramount 
duty  is  to  see  that  workmanship  is  of  highest  class,  that  materials  used  meet 
all  prescribed  tests,  and  that  the  general  intent  of  the  specification  describing 
cable  being  manufactured  is  adhered  to.  Results  of  the  more  important  tests 
are  recorded  and  a  copy  of  this  record  forwarded  to  the  Chief  Signal  Officer  of 
the  Army,  who  has  it  placed  in  the  archives,  where  it  may  be  referred  to  should 
occasion  for  such  action  arise.  A  tag  bearing  order  number,  inspector's  initials, 
and  date  of  acceptance  is  attached  to  reel.  This  tag  is  in  addition  to  brass 
tag  bearing  Signal  Corps  number,  which  has  previously  been  described. 

In  view  of  the  above  it  is  safe  to  assume  that  new  cable  is  of  the  best 
quality,  everything  considered,  and  it  only  remains  necessai*y  to  install  and 
splice  it  properly  in  order  that  this  very  important  part  of  an  electrical  system 
will  be  of  the  highest  standard. 

If  any  recovered  cable  is  furnished,  a  preliminary  test  of  it  before  installation 
should  be  made,  and  cable  that  does  not  appear  to  be  iu  excellent  condition 
mechanically  or  electrically  should  not  be  used. 

After  the  cables  have  been  pulled  in  ducts  and  splices  and  pot  heads  placed, 
the  person  in  charge  of  the  installation  or  an  assistant  will  test  each  com- 
pleted cable.  Each  conductor  is  assigned  a  number.  The  tests  of  the  com- 
pleted cable  will  show  insulation  resistance  of  each  conductor,  electrostatic 
capacity  of  each  conductor,  and  ohmic  resistance  of  each  conductor.  When 
tests  are  made  the  tester  carefully  records  data  obtained  in  a  field  book  and 
when  convenient  computes  values  and  enters  them  on  Signal  Corps  Blank  Form 
No.  261,  issued  for  the  purpose. 

AVith  cables  of  short  length  it  is  difllcult  to  obtain  readings,  due  to  high 
value  of  insulation  and  low  value  of  electrostatic  capacity,  and  therefore  it 
is  not  necessary  that  actual  values  be  recorded.  A  statement  in  effect  that 
each  conductor  has  an  insulation  equal  to  500  megohms  per  mile  or  that  the 
tester  was  unable  to  obtain  deflection  on  the  galvanometer  will  be  sufficient. 

Ohmic  resistance  of  conductors  should  be  recorded. 

These  tests  will  disclose  the  condition  of  each  completed  cable  of  the  system 
and  will  show  whether  or  not  defective  splices  or  pot  heads  have  been  made; 
also  whether  or  not  the  cable  has  been  injured  in  pulling  it  into  the  conduits. 
This  is  especially  true  if  the  cable  has  been  sifl).1ected  to  moisture,  <lue  to 
rain  or  otherwise,  after  all  splices  have  been  completed.  The  reason  for  this 
is  obvious,  as  it  can  be  readily  understood  that  a  hole  in  the  lead  sheath 
would  not  affect  the  insulation  resistance  of  a  cable  if  the  cable  at  that  point 
is  kept  absolutely  free  of  moistur(\ 

The  exacting  methods  employed  in  making  the  factory  test  sliduld  be  ignored 
in  making  this  field  test.  This  means  that  no  correction  should  be  made 
for  temperature  w  for  the  one-tenth  megohm  resistance  usually  left  in  series 
with  insulation  resistance  bcMug  measured. 

(Corrections,  bcnvever,  sh(»ul»l  be  made  for  insulation,  capacity,  and  ohmic 
resistance  of  leads  if  it  is  lound  (hal  iilliiiiate  values  are  materially  affected 
by  these  values. 


Cable  and  Cable  Systems. — Chapter  4.  39 

For   acconiplisliiiij,'    tlic    tests    just    uifiitioiu'd    the    .Signal    Corps    issues    an 
electrieal  instrinnent  case. 

The  contents  of  this  case  are  as  follows : 

KLECTRICAL    INSTRUMENT    CASE. 
[This  Instrument  ease  Is  manufaetiired  under  specification  No.  140.] 

COXTHXTS. 

One  insulation  and  capacity  test  set,  con.sisting  of  the  following  in  case: 
1  portable  galvauouieter  of  the  D'Arsouval  type,  conforming  to  that  shown  in 

figure  4-30. 
1  telescope  and  scale  for  above  galvanometer. 
1  ]()().0(»0-ohm  box. 
I  combined  shunt   ai.d  switch. 
1  condenser  st't. 
1  ohmmeter. 

1  tripod,  external  to  case. 

1  service  testing  battery,  drawing  No.  199/),  specification  No.  185. 
1  micrometer  caliper,  without  ratchet  stop,  with  morocco  carrying  case. 
1  inspector's  pocket  tool  kit,  as  per  drawing  No.  204,  specification  No.  186. 
1  testing  telephone. 
1  space  for  forms  and  reports. 
1  space  for  books. 

MISCELLAXEOl'S  PARTS  A.ND  SUPPLIES. 

1  galvanometer  coil  and  mirror. 
4  round-head  plugs. 

6  lower  suspensions. 
6  upper  suspensions. 

2  milled-head  screws. 
1  piece  felt. 

4  screws  for  glass. 

1  ohmmeter  card. 

1  piece  chamois. 

1  bottle  vaseline. 

1  bottle  typewriter  oil. 

KKl  feet  No.  22  bare  copper  wire. 

1(K>  feet  advance  wire.  No.  28. 

25  feet  No.  22  manganln  wire. 

l.">0  feet  No.  34  nianganin  wire. 

300  feet  No.  40  manganin  wire. 

fiO  feet  No.  28  manganin  wire. 

1  glass  window. 

4  paper  scales. 

n  feet  battery  cord. 
10  feet  okonite  wire. 

5  ounces  solder. 

REPAHl    KIT. 

The  repair  kit  contains  the  following  instruments' 

1  nickel-plated  screw  driver. 

2  pairs  tweezers,  nickeled. 

3  lower  suspensions  for  galvanometer. 

4  upper  susjiensions  for  galvanometer. 

46581°— 17 10  (139) 


40 


Signal  Corps  Manual  No.  3. — Chapter  4. 


Description  of  tlie  various  instruments  follows. 

THE   GALVANOMETER. 

A  reflecting  D'Arsonval  galvanometer  is  supplied,  arranged  for  mounting 
on  a  tripod.  It  is  provided  with  a  short  insulated  telescope  arm  and  an 
optical  system,  which  magnifies  the  image  of  the  scale.  Owing  to  this  magni- 
fication, it  is  necessary  to  mount  the  instrument  on  a  solid  floor  or  to  provide 
against  jars  while  testing,  which  tend  to  make  the  image  indistinct. 

As  'in  all  the  instruments  of  this  type,  the  frame  forms  conductor  for  one 
side  of  the  circuit,  and  the  tripod  legs  should  be  wiped  thoroughly  dry  before 
making  a  test.    This  precautionary  measure  should  always  be  taken. 

The  sensibility  of  this  instrument  is  300  megohms.  This  is  determined  l)y  the 
fact  that  one  volt  through  one  megohm  will  deflect  the  mirror  300  scale  divi- 
sions.    Figure  4-30  shows  the  construction  of  this  instrument. 


FRONT 


era      Thin  UotJt  glued 

olJH    to  this  before  yyrwmfom 

DETAILS  OF  CLAMP 
Fig.  4-30.— GALVANOMETER,    REFLECTING,    DARSONVAL  TYPE. 

( I  nil 


Part 
No. 


17 


1 
2 
3 
4 

5. « 
7 
S 
9 
10 
11 
12 
13 
14 
15 
Iti 
,1S 
19 
20 
21,22,23 
24 
2", 

2t) 

27 

2S 

29 

30 

31,32 

33 

34 

35 

36 

37 

38 

39 

40 

41 

42,43,44, 

45,46,47 

48 

49 

50,51,52 

53,54,55 


Cable  and  Cable  Systems. — Chapter  4. 

(Seeng.  4-30.) 


41 


Name. 


Torsion  head  and  screw 

Torison  rod 

Tube 

I 'pper  suspension 

Suspension  heads 

Mirror , 

Upper  chuck  and  screw 

Coil 

Masnetic  core 

Lower  suspension  with  heads . 

Lower  chuck  and  screw 

Field  maKiiot 

Front  cover  and  screws 

Rear  co\er  and  screws 

Dampening  device 

Terminals 

Telescope  rest  and  screws 

Steady  pin 

Leveling  screws 

IJase 

Telescope  arm 

Arm  screw 

Telescope  screw 

Telescope  barrel 

Ivcns 

Diaphragm 

Truiuiion  screws 

Telescope  frame 

Scale-adjusting  screw 

Scale  frame 

Scale 

Insulating  joint 

Tripod  head 

Upper  legs,  triijod 

Lower  legs,  tripod 

Clamp 

Clamping  screws 


Wing  nut 

Base  screw 

Spurs 

Hinge  screws  and  springs. 


Reference 
No. 


21 


1 

2 

3 

4 

5,6 

7 

8 

9 

10 

II 

12 

13 

14 

15 

16 

17.18 

19 

20 

,22,23 

24 

25 

26 

27 

2S 

29 

30 

31,32 

33 

34 

35 

36 

37 

38 

39 

40 

71 

43.44, 

.46,44 

48 

49 

.51,52 

,54,55 


100,(U»0-OHM   BOX. 

Tin'  l(M»,(KHt-(iliiii  l)(ix  is  a  circular  rubV>er  ease  liavliij,'  niouiilcil  ilicii'iti  lo  coils 
wound  with  No.  40  !>.  &  S.  uiaujianin  wire.  Sliould  tn)ul)le  oc<ur  with  this 
(knice  tlie  proper-sized  wire  will  be  found  in  tlie  spare-parts  case,  'i'liis  box 
is  held  t<i;rether  with  two  .screws.     {F'lix.  4-:U.) 


Fig.  4-31.— BOX,    100.000  OHM..  STANDARD. 
(141) 


42 


Signal  Corps  Manual  No.  3.— Chapter  4. 


COMBINEU    SHUNT    AND    KEY. 

This  sluiiit  nnd  koy.  or  button,  takes  the  place  of  the  usual  Ayrton  shunt, 
hattery  key,  anil  short-t-ircuit  key.  Its  connections  and  general  construction 
are  shown  in  figure  4-3"2. 


^Knurled 


Fig.  4-32.— SHUNT  AND   KEY. 

The  key  is  provided  with  a  bayonet  joint.  Tlie  sliunt  sliould  always  be  on 
0.(X>01  at  tile  l)eginning  of  tlie  reading,  and  tlie  lower  l)utton  is  tlien  turned  until 
a  readable  dellection  is  obtained. 

The  button  B  controls  the  battery,  and  the  button  »S  controls  the  shunt. 

This  method  of  operating  the  galvanometer  insures  against  sudden  heavy 
currents  and  consequent  violent  disturbance  of  the  moving  system  incident 
to  low  insulation  and  dispenses  with  the  short-circuit  key. 


btCTlON 

Fig.  4-33.— CONDENSER,   STANDARD. 


(142) 


Cable  and  Cable  Systems. — Chapter  4 


43 


STA  N  DA  i:i>    (  ( »M»i;.N  SKIC. 

Tlic  stiiiitlanl  coiKlciiscr  set  consists  (if  a  unc-tliii'fl  nii<Tnfiii'a<l  ii<>ii;i(|.inslii- 
Itk'  cdndcnst'i*,  with  a  l<»^v  lor  its  oprration.  an«l  tiic  necessary  liiinlin;:  posts 
and  pliij,'s,  as  sliown  in  tiunrc  4-.'};{.  Its  conn«'ctions  arc  also  sliown  in  the 
li};ure.  Hy  niovint:  tlie  switcli  N  to  the  rijilit  either  liie  calile  or  condenser  may 
he  char;;ed,  (h'i»cndin.ir  on  tlie  location  of  tlie  phi;r.  Tiie  condenser  is  of  l»<'st- 
firade  mica,  wiih  n'<iri  and  beeswax  tillin;;. 

SKRVU'E-TKSTl  \(!    ItATTKUY. 

The  service-tostiiiLC  l)attery  consists  of  1(H)  cells  o!"  simmII  dry  hMlteries.  (Fit:. 
4-,'U. )     They  should  l»e  examined  once  a  month. 

The  battery  is  tapi»ed  for  ".,  ](>,  2.").  fid,  7."..  and  KHt  cells.  When  new  it  should 
have  an  K.  M.  F.  I>etweep.  140  and  "i">0,  and  slioidd  not  drop  below  KX*  within 
a  year.  When  certain  cells  show  deterii>ration  they  should  be  removed  and  the 
circuit  restored.  New  cells  throujihout  should  be  rtHpiisitioned  for  when  a 
majority  of  the  cells  show  discoloration  and  the  voltage  of  the  whole  battery  is 
under  80  with  all  connections  in  good  order  and  the  poorest  cells  cut  out. 

Care  must  be  exerci.sed  to  keep  the  battery  connections  clear  of  short  circuits, 
as  the  total  hiph  voltajre  will  cause  a  heavy  current  to  flow  and  ruin  the  bat- 
tery very  (|Uickly  if  cnnnectcnl  to  a  circuit  of  low  resistan<-c. 


®_Q_®[ 


Q®i  y 


0  o  <S>| 


SECTION 

Rg.  4-34.— UATTERY,  SERVICE.  TESTING. 


(14:Vl 


44 


Signal  Corps  Manual  No.  3. — Chapter  4. 


OHM  METER.     MODE),     llt04. 

Tlieoliiiimoter  1'iiniislml  with  this  case  is  a  <-(iiiipact  form  of  tlio  orisinal  nioclel 
olimiueter.  The  variable  resistance  is  wound  on  a  cylinder  so  arranjied  as  to  he 
divided   into  l.UOO  iniuai   parts  by   a   horizdutal   scab'  of  20  (-(lual   i)arts  and   a 


I  h  Batiery  external  to  instrument 


(^^Q^OJ 


H3 


PERSPECTIVE  VIEW 


?; 


•^  ^ey 


J 


( Sliding  resistance  1 

CIRCUITS  OF  OHMMETER 


PLAN  WITH  COVER  OPENED 

Fig.   4-35.— OHMMETER,    MODEL    1904. 

drum  srale  of  .'0  unit  parls.  Tlic  rcaiiinir  oblained  from  tlic  slyliis  is  arbitrary, 
jitid  referenc*'  is  lia<l  (o  Ihc  table  in  tlie  <-ov<'i-  of  tlic  iust  niiuent  lor  the  actual 
resistance  corresponding  to  aiiv  vi\''n  position  of  Ihc  sll.vns.  (Sec  lijj.  4-85.) 
'IMic  batlcrv  kev  has  a  bayonci    calcli. 


(144) 


Cable  and  Cable  Systems. — Chapter  4. 


45 


CABLE-TKSTINfi   TKLKFMIONK. 

This  telcphuno  was  designed  in  tlic  engineering;  division,  Signal  Uilice,  fur 
use  of  cable  testers,  and,  as  will  lie  noted,  is  especially  arranged  for  this 
work.     (See  figs.  4-36  and  4-37.) 

The  home  station  is  provided  with  lour  cells  of  4-0  battery,  a  pony  relay,  a 
buzzer,  a  choke  coil,  an  interrupter,  and  a  hand  set.  The  distant  station  has  a 
hand  .set  and  a  resistance  of  500  ohms  normally  in  circuit  with  it,  but  this 
resistance  may  be  cut  out  by  depressing  the  switch  in  the  handle  of  tlie  set. 

When  the  home  operator  wishes  to  call  the  distant  station  he  draws  out  the 
ring  of  the  interrupter,  which  causes  the  distant  receiver  to  rattle.  When  the 
distant  operator  picks  up  his  hand  set  and  closes  the  switch  in  the  handle, 
short-circuiting  the  otK)  ohms  at  the  distant  telephone,  the  home  relay  operates, 
closing  a  local  buzzer  circuit  and  causing  the  buzzer  to  vibrate.  When  the 
home  operator  depresses  his  switch  in  tlie  hand  set,  tlie  buzzer  is  cut  out  of 
circuit  and  conversation  may  take  place.  The  distant  hand  switch  is  used  for 
calling  only. 


Fig.  4-36.— TELEPHONE.    CABLE  TESTING. 


Part 
No. 


Name. 


Reference 
No. 


Case 

Battery  (4  cells  of  4-o). 

Pony  relay 

Buzzer. 


Choke    coil „ 

Intermpter , 

Hand  set ,  home  station  (switch  in  handle) 

Hand  set,  distant  station  (switch  and  500  ohms  in  handle). 
Cord  for  liand  set 


(14.")) 


46 


Signal  Corps  Manual  No.  3. — Chapter  4. 


METHOD    OF    MAKING    FIRST    TEST    AFTER    INSTALLATION. 

The  tester  should  have  two  assistants.  One  should  he  a  man  faniiliar  with 
electrical  apparatus.  The  cable  tester  should  proceed  to  a  point  from  which 
a  number  of  cables  radiate.  The  more  experienced  assistant  should  be  sent 
to  distant  end  of  cable. 


Fig.  4-37.— TELEPHONE,  CABLE  TESTING,  CIRCUITS. 


DUTIES   OF   TESTER. 


The  galvanometer  should  he  set  up  dii  solid  foundation  in  such  relation  to 
the  strongest  lif,dit  that  the  .scale  is  most  ilUnninated  wliile  the  mirror  is  in 
the  shadow.  The  box  containing  the  insulation  and  capacity-testing  set  should 
l>e  placed  on  a  dry  foundation.  Tiie  lOO.OOO  ohm  box  should  be  wired  perma- 
nently into  circuit,  to  avoid  dangerous  currents,  and  should  al.so  be  placed  on 
a  dry  foundation. 

Ordinarily  it  is  advisable  to  thoroughly  insulate  the  battery.  This  may  be 
accomplished  by  placing  a  piece  of  heated  glass  between  battery  and  support 
or  by  susi)ending  the  battery  from  ceiling  by  means  of  a  wire  or  cord,  with  a 
luniiber  of  iioi-ci'lain  knobs  connected  in  each  hanger  in  such  a  manner  that  the 
<'ord  or  wire  is  not  in  one  continuous  ])ie<'e.  A  torch  may  be  ai)pli(Hl  occa- 
sionally to  tlie.se  porcelain  knobs  in  order  to  disperse  the  slightest  tilm  of 
moisture  that  nuiy  collect. 

While  the  tester  is  setting  up  (he  instrumenl.s,  his  assistant  should  get  the 
cable  ready  for  test.  The  assistant  at  the  distant  end  of  the  cable  should  have 
been  instructed  to  clear  the  ends  of  all  conductors,  .scraping  them  carefully  and 
taking  care  to  keep  them  dry  and  clear  of  each  other  and  ground,  while  the 
test  of  insulation  and  electrostiitic  capacity  is  in  i)rogress.  In  some  instances 
It  is  necessary  to  apiily  the  Ilame  of  n  small  alcohol  torch  to  the  ends  of  the 

(146) 


Cable  and  Cable  Systems. — Chapter  4.  47 

conductors  in  onlt-r  to  dissiimt*'  :ill  niDisiiirt'.  IT  lliis  is  rcsortcij  In,  ^iicit  <iiro 
siiould  Ih'  takfn  to  avoid  <»\i'rlieatin;;  tlu'  insuialioii,  as  it  will  n'sull  in  sliow- 
iiiK  coniimratively  heavy  iealva«e.  A  ;,'asolint'  llanic,  or  any  llainc  wliicli  will 
smoke  the  ends  of  conductors,  sliould  not  l)e  used. 

The  testinfc  telepiione  may  t>e  used  in  connection  wilii  identiliiation  of  con- 
ductors on  h>nK  caldes,  especially  those  havinj;  rubber  insulation  or  whenever 
connnunication  between  tester  and  his  assistant  at  opposite  em!  of  the  cable  is 
desired. 

In  testing  short  subterranean  cables  a  satisfactory  substitute  for  this  tele- 
piione for  the  purjiose  mentioned  above  is  two  Coast  Artillery  type  head  sets,  one 
of  these  head  sets  to  be  used  at  each  end  of  tlie  cable.  To  use  these  head  sets  as 
a  telephone,  tie  back  out  of  the  way  the  common  wire  (black)  of  each  head  set, 
as  this  wire  is  not  used.  Connect  either  of  the  two  renuiining  wires  (red 
and  yellow)  of  one  of  the  head  sets  to  cable  sheath  in  series  with  two  cells  of 
dry  batteries,  the  other  wire  to  he  attached  to  conductor  over  which  it  is  desired 
to  conmmnicate.  The  other  head  .set  at  opposite  end  of  cable  is  conne<'ted 
similarly,  except  that  the  cells  of  dry  battery  are  onntted. 

Identification  of  conductors  can  very  quickly  be  made  by  this  means,  as  it  is 
only  necessary  for  tester  to  connect  one  wire  of  his  head  set  to  a  conductor 
of  cable  anil  assistant  at  other  end  to  slide  one  wire  of  his  head  set  over 
conductors.  When  the  conductor  selected  by  tester  is  touched,  the  assistant 
receives  a  loud  click  in  the  receiver  of  his  head  set.  He  immediately  touches 
the  wire  again  and  responds  with  "  Hello  "  in  the  mouthpiece  of  the  transmitter. 
The  tester  assigns  a  number  to  the  conductor  used.  Immediately  following 
this  procedure  the  tester  disconnects  wire  of  head  set  from  cable  conductor 
and  connects  it  to  another  conductor.  The  operation  is  repeated  until  numbers 
have  been  assigned  all  conductors  of  the  cable  being  tested. 

A  check  test  should  then  be  made.  This  can  be  very  (juickly  accomplished, 
as  it  should  not  be  necessary  to  hunt  for  conductors. 

Having  identified  all  conductors,  the  tester  instructs  the  distant  assistant 
to  see  that  all  wires  are  clear,  except  one  used  for  the  telephone,  and  then  to 
report.  When  all  are  reported  clear,  the  assistant  may  be  instructed  to  stand 
by  and  await  orders;  under  no  conditions  to  tou<b  the  cleared  wires  uidess  told 
to  do  so. 

INSULATION    MEASUREMENTS. 

THE    author's    explanation    OF    PRINCIPLE    INVOLVED    IN    MAKING    INSI-L.\TION 
RESISTANCE    MEASITtEMENTS. 

The  method  employed  is  a  comparison  of  insulation  resistance  value  of  cable 
with  a  known  resistance.  In  order  to  make  this  comparison  it  is  necessary  to 
know  the  number  of  divisions  dellection  on  galvanometer  scale  that  will  be 
obtained  when  a  current  of  uniform  strength  is  caused  to  flow  through  the 
known  resistance  and  the  galvanometer  coil  in  series.  It  must  be  rememberetl 
that  the  detlection  of  galvanonu'ter  arnuiture  is  dependent  uiH»n  the  strength  of 
current  that  is  tlowing  through  its  coil  <ir  winding  and  that  strength  of  dire<;t 
current  in  any  circuit  is  dei>endent  on  E.  M.  F.  and  resistance  of  circuit. 

When  the  miml)er  of  divisions  dellection  through  a  known  resistance  is  known, 
it  is  merely  necessary  to  compare  the  divisioiLs  detU'ction  obtained  through  an 
unknown  resistance  with  the  former  to  determine  value  of  unknown  resistance. 
Exami)le:  If  a  .scale  dellection  of  10  tlivisions  is  obtained  through  1  ohm  and  a 
deflectiiUi  of  2  divisions  is  obtaintMl  through  insulation  of  cable,  what  is  insula- 
tion resistance  of  cable?  Ten  divisions  dividtnl  by  li  divisions  «Miuals  ."i.  there- 
fore only  one-tifth  as  many  tlivisions  detlei-tiou  is  obtaine<l  through  the  insula- 
tion of  the  cable  as  that  obtained  through   1  ohiiL  conse<iuently  the  insulation 

(147) 


48  Signal  Corps  Manual  No.  3. — Chapter  4. 

resistance  of  cable  must  be  tive  times  1  ohm,  oi*  5  ohms.  Now,  assume  this  cable 
to  be  2  miles  long  and  it  is  desired  to  determine  the  insulation  per  mile  of  such 
a  cable.  If  sufficient  current  can  escape  through  2  miles  of  the  insuhition  to 
establish  a  value  of  5  ohms  insulation  resistance.  1  mile  of  such  insulation  would 
allow  only  sufficient  current  through  it  to  show  two  times  as  high  a  resistance, 
or  5  ohmsX2=10  ohms,  the  insulation  resistance  of  such  cable  per  mile. 

While  the  foregoing  clearly  demonstrates  the  principle  involved  in  computing 
insulation  measurements,  the  values  usually  encountered  are  very  much  higher. 
For  instance,  the  Signal  Corps  specifications  require  certain  cable  to  have  an 
insulation  resistance  of  at  least  1.400  megohms  per  mile.  One  megohm  equals 
1.000.000  ohms.  The  reader  can  readily  understand  that  in  measuring  such 
values  it  will  be  advantageous  to  know  the  divisions  deflection  through  a  much 
higher  resistance  than  1  ohm,  consequently  the  standard  used  is  100,000  ohms, 
or  Tts  megohm.  In  measuring  high  insulation  values  a  battery  of  high  voltage 
must  be  used,  as  with  exceedingly  high  insulation  resistance  a  deflection  of 
one  division  on  the  galvanometer  scale  will  not  be  obtained  unless  high  E.  M.  F. 
is  used,  for  it  must  be  remembered  that  divisions  deflection  is  dependent  upon 
current  strength,  and,  according  to  Ohm's  law,  current  strength  equals  electro- 
motive force  divided  by  resistance  in  ohms. 

Assume  that  a  deflection  of  10  scale  divisions  was  obtained  in  measuring 
the  insulation  of  a  cable,  that  the  insulation  value  was  1,000  megohms,  and  that 
the  known  resistance  was  ttj  megohm ;  referring  to  the  first  example  quoted  in 
the  foregoing  and  working  backward,  we  will  find  that  the  divisions  deflection 
obtained  when  the  known  resistance  was  measured  was  100,000  divisions. 

It  is  impracticable  to  construct  galvanometers  with  such  a  range,  consequently 
an  instrument  termed  a  shunt  is  used,  and  by  its  means  only  a  known  fraction 
of  the  current  in  the  circuit  is  passed  through  the  galvanometer.  These  shunts 
are  usually  made  so  the  fraction  can  l)e  changed  at  will  and  any  one  of  the 
following  fractions  of  cun-ent  passed  through  galvanometer,  A,  rh^j  -nrinr)  iTraTJ^- 
As  previously  stated,  the  divisions  deflection  are  directly  proportional  to  current 
.strength,  therefore  if  10  divisions  are  obtained  when  ^  shunt  is  used  the  true 
deflection  is  ten  times  as  great,  or  100. 

Let  us  now  refer  to  the  last  example  and  assume  that  in  measuring  through 
the  known  resistance  {^  megohm)  the  xrnrff  shunt  was  used.  If  the  true 
deflection  was  100.000  divisions  the  deflection  obtained  using  the  j^uis  sbunt  was 
one  one-thousandth  of  the  true  deflection  or  100,000  divided  by  1.000  equals 
100  divisions  (a  fair  scale  reading). 

In  observing  the  reading  on  known  resistance,  where  the  lowest  fractional 
proportion  of  the  shunt  will  not  restrict  the  reading  to  the  scale  of  the  galva- 
nometer wlien  using  the  battery  to  be  employed  in  taking  the  reading  on  insula- 
tion of  cable,  it  is  necessary  to  reduce  the  voltage  of  the  battery  and  again  in- 
crea.se  it  when  reading  is  made  on  insulation  of  cable. 

V, 

Again  referring  to  Olini's  l:i\\   1  tlH-rcforc  the  current  flow  is  also  directly 

proportional  to  llic  voltage  imi)ress('(l  on  the  circuit.  If  a  voltage  of  10  volts 
is  used  in  obtaining  dclU-clion  with  known  resistance  and  100  volts  is  used  in 
obtaining  deflection  wilh  insulation  of  cable,  the  true  detleclion  on  the  known 
resistance  will  be  ten  times  the  one  obfaiiieti,  as  the  voltiige  of  the  latter  is  ten 
times  as  great.  HMius  it  will  l»e  seen  that  in  measuring  high  insulation  re- 
sistance the  divisions  dellection  through  insulation  are  observed  with  full  value 
of  liattery  and  witii  galvanometer  unshunted  so  tii.if  I'nll  strength  of  current 
flows  through  galvanometer  armature  winding;  it  will  also  be  observed  that 
in  obtaining  divisions  dellection  tliioii-li  .-i   Unown  resistance  llie  galvanometer 

(H8) 


I 


I 


Cable  and  Cable  Systems.-^Chapter  4. 


49 


is  shunted  or  hattory  vollaf^o  reduccHl.  ny  hudi,  and  that  tlierefore  it  is  nect^s- 
sary  to  coniputc  in  oidci-  to  ohtain  the  true  deflection  that  would  obtain  were 
ronditions  similar  lo  lliose  wlien  deflection  throujrh  insuhition  resistance  is 
((bserved. 

The  operation  of  findiii;;  the  scale  divisions  deflection  throufih  a  known  re- 
sistance is  termed  "  r>etermining  the  s:ilvanonieter  constant."  This  constant 
is  expressed  in  the  numljer  of  mejrohms  that  would  l)e  in  the  circuit  when  a 
true  deflection  of  one  scale  division  is  obtained  or  number  of  true  scale  divisions 
deflection  that  would  be  obtained  in  measuring  through  1  megolim  i-esistance. 


Com  b'ned  Shun  land  Key 


\D,suinten<3  of  cable         CorauUor-p&>c,i!e^-fjrU:LC  ' 
Fig.  4-38.— CABLE  TESTING,    GALVANOMETER   CONSTANT. 


The  sensibility  of  a  galvanometer  is  expressed  in  meghonis.     It  is  the  number 
of  megohms  required  in  the  circuit  to  give  a  reading  of  one  scale  division 
using  a  battery  voltage  of  1  volt.     Example:   Using  battery  of  100  Y,  ^^If,^ 
shunt  and  t^  megohm  as  known  resistance,  a  deflection  of  30  divisions  is  ob- 
tained, what  is  sensibility  of  galvanometer? 
(d)=Divisions  deflection, 
(s)  =^Iultiplying  jiower  of  shunt. 
(v)=  Voltage. 
(kr)^Knovvn  resistance  in  megohms. 

rrX  s  X  kr  X  (l=me<j;olim.s  sen.'^ibilify  (or  di^i.^ion?  deflection  through  1  megohm) 
8ub.stituting  the  above  values: 

jqqX  10000  XjqX30=.SOO  divi.sinn.>^  through  I  megohm  at  1  volt.  This  is  equiv- 
alent to  1  division  through  ;i00  megohms  at  1  volt.  Therefore  the  sensibility  of  gal- 
vanometer is  300  megohms. 


(149) 


50 


Signal  Corps  Manual  No.  3. — Chapter  4. 


COUKECTION    KOI!    l.KADS. 

Oil  iirt'pjiriiij,'  Tor  readings  of  insulation.  (•ai)acit.v,  and  copjior  n'sistanfe, 
readin;,'s  .sliould  1)0  taken  for  each  of  these  value.s  on  the  leads  and  recorded 
for  correction  of  the  respective  test  readin&s. 

TO     DETERMINE    THE     GALVANOMETER     CONSTANT. 

The  tester  proceeds  to  get  his  s:^lvanometer  constant  for  insulation,  as 
follows : 

With  connections  as  shown  in  figure  4-8S,  he  moves  the  sluint  to  0.0001 
and  depresses  the  battery  key  on  sluint.  The  constant  is  then  determined 
by  dividing  the  resulting  deflection  by  the  shunt  value  and  then  dividing  l)y  10, 
the  standard  resistance  box  being  only  100,000  ohms  insteiid  of  1  megohm. 
This  gives  the  deflection  which  the  battery  used  would  cause  through  1  megohm 
without  shunt. 


^. 


Combined  Shunt  and  Key 


,^^^M^^ 


*-}9  Qqq,aQ. 


Seri'ice  TestJng  Battery 


C>:.tanL  end  oFcoble         Conaudor  ■pencilled' for  fci  t 


Fi(?.  4-39.— CABLE   TESTING,    INSULATION. 

It  is  most  important  to  us(>  the  same  battery  voltage  in  testing  fts  in  deter- 
mining the  constant,  or  make  due  allowance  for  change  of  voltage  in  com- 
puting test  results.  For  insulation  tests  it  is  customary  to  utilize  a  voltage 
of  ai)i)roximat('l,\    ion. 

INSULATION    TEST. 

Connections  ww  llim  made  as  shown  in  figure  4-.^0.  Tliis  comiection  puts 
till'  galvanomeltT  :iiid  hallcry  in  scries.  Ihrough  the  shunt  and  100.000-ohiu 
ito\,  Willi  llif  conductor,  its  insulation  throughout  its  whole  lenglh  and  ground. 
All  I  he  (itlicr  (■undiict(»rs  of  the  cable  sh(»uld  also  be  connected  to  ground.  The 
test  is  liierefore  against  all  the  other  conductors  ;ind  ground,  tlius  de(«'rmining 
tlie  existence  of  crosses  between  conductors  as  well  as  insulation  t«i  gn»und. 

(ir.O) 


Cable  and  Cable  Systems. — Chapter  4. 


51 


Havin;,'  roiiiit'itcil  tlius  t<i  Nd.  1  cumliictor,  (lie  slmiit  is  set  at  O.fKM)!  ami  the 
battery  Imtton  dcinH'ssed.  Willi  niiilier  cables  an  electrification  of  one  minute 
is  desirable.  In  paper  cal)le  the  electrification  is  practically  instantaneous,  and 
the  slnmt  may  be  moved  to  j;radually  smaller  values  until  a  readable  deflection 
Is  obtained.  The  deflection,  shunt,  and  conductor  numbr-r  are  then  entered  in 
a  notebook,  and  if  the  readin;?  is  nonnal  (lie  <ntidii<li>r  is  rci)hiced  in  the  biMMJi 
and  the  next  one  is  tested. 

On  comparatively  short  caltles  where  exact  i'eadiMj,'s  are  impracticable  .'{o 
seconds'  electrification  is  suflicient. 

Should  trouble  be  found,  the  assistant  shoubl  be  called  and  asked  to  scrape 
the  insulation  of  the  conductor  in  question  carefully  and  see  that  it  is  free. 
Havins  identified  all  wires,  it  is  a  simple  matter  to  te.st  the  telephone  wire  by 
substituting  for  the  telephone  line  one  of  the  wires  fir.st  tested. 


Dtatont  c/jrf  of  Cjb' 


Fig.  4-40.— CABLE  TESTING,    CAPACITY. 


The  followiii;:  exami)le  is  submitted  to  indicate  the  method  of  calculating 
the  insulation  resistance  of  a  cable. 

Suppose  our  deflection  Ihroujrh  ]()O,(H»0  ohms,  using  O.lMMll  shmit,  to  be  S() 
divisions,  then  the  constant  equals  SO  divided  by  O.tKX)!  and  multiplied  by 
one-tenth.     Constant  tHpials  80,000. 

Suppose  our  detlection  on  conductor  No.  1  is  40,  with  a  shunt  value  of  1  : 
then,  since  the  constant  is  the  deflection  through  1  megohm,  the  number  of 
megohms  represented  by  this  deUection  will  be  S0,(MK1  divided  by  4U,  or  •J.fKKl 
megohms. 

If  the  cable -were  IJ  miles  long,  to  reduce  this  value  to  megohms  i>er  mile 
it  would  be  necessary  to  multiply  it  by  li,  and  the  insulation  resistance  iwr 
mile  would  be  3,000  megohms,  an  average  value  for  paper-insulation  cables 
not  including  pot  heads  under  usual  weather  conditions. 

Tlie  conductors  of  all  completed  cables  of  systems  using  new  <-able  should 
show  an  insulation  resistance  of  at  least  .100  megohms  per  mile.  The  con- 
ductors of  all  completed  cables  of  systems  using  re<'overe<l  cable  should  sliow 
an  insulation  resistance  of  at  least  3(M1  megohms  i»er  mile. 


52 


Signal  Corps  Manual  No.  3. — Chapter  4. 


CAPACITY    TEST. 

Having  obtained  tlie  insulation  resistance  of  all  the  conductors,  the  battery 
is  disconnected,  the  100,000-ohm  box  is  set  aside,  and  the  condenser  set  is  con- 
nected as  shown  in  figure  4—40.  The  condenser  set  is  held  in  the  hand  or  may 
be  placed  on  table.  If  the  latter  is  resorted  to,  the  condenser  should  be  placed 
between  cleats  fastened  to  table  in  order  that  switch  of  set  may  be  positively 
and  quickly  operated.  Suitable  battery  (not  more  than  5  or  10  cells)  is  con- 
nected to  the  condenser.  The  deflection  on  the  standard  condenser  is  then 
compared  with  the  deflection  caused  by  the  cable,  using  the  same  battery  and 
shunt  value. 

The  following  example  shows  the  method  of  calculating  capacity : 

Suppose  the  deflection  through  the  standard  condenser  were  150  and  the  leads 
were  negligible. 

Suppo.se  our  deflection  througli  the  cal)le  wore  4.1(1. 

w  w 


Fig.  4-41.— OHMMETER,    THEORY,  •    ' 

Tlie  cajjacity  of  (lie  (■■,\\)\r  would  then  be  4r)0  divided  by  1.10,  or  8  times  the 
capacity  of  standard  (one-third  M.  F.).  The  cable  capacity  therefore  would 
lie  1   microfarad. 

If  the  cable  were  2  miles  long,  its  capacity  per  mile  would  be  1  divided  by 
2,  or  O.n  microfarads,  a  little  above  the  average  for  rubber  cable. 

OHMMKTEli,     MODKI,     1!»04. 

The  Iheoretical  diagram  of  the  olinMiicIci-.  model  1004,  is  given  in  figure  4-41, 
ill  uliicb  the  i)arts  of  the  conventional  form  of  llie  Wheatstone  bridge  are 
iilipiirent.  The  ,1  and  /{,  or  "  bii lance  arms,"  are  the  two  jiiirts  of  the  bridge 
wire   W   W  into  which  it   is  divided  by  the  "  toucher." 

The  two  standard  resistiince  coils  1((  mikI  100  ohms,  respectively,  correspond 
to  the  R  arm  of  the  bridge,  .V  (the  uid<n<»wii  resistance)  forming  the  other  arm. 
Tli(!    telephone    receiver    may    tMke    the    pliice    of    the    gidvanometiT,    balance 


(tr.2) 


Cable  and  Cable  Systems. — Chapter  4. 


53 


lioiii;,'    indicalcd    by    tlic   ci'ssiition    of   tlic    clicks   jiiid    fryiii;:   soiiml    wlieii    tlie 
loiulior  liiis  reuclied  the  proper  graduation  on  the  bridge  wire. 

niKECTIONS    FOK    USING    THP:    OIIMMKTKU,     MODKI.     I'.HIl. 

Connect  a   battery.   |)referaltly  a   couple  of  dry   cells  external    Id   the  testing 
set,  to  posts  marked  ■"  I'.al."  and  the  niikiinwn  resistance  to  jiosts  A'l.  A'-.     If  the 


Sliding  fi£,si stance 

mmmmmm^ 


Distant  end  of  cable 
Fig.  4-42.— OHM  METER,    RESISTANCE    MEASUREMENT. 

resistance  is  small,  insert  the  plug  at  10  and  if  large  at  100.  Depress  the 
key  and  operate  catch ;  then  draw  the  stylus  liyhtly  across  the  horizontal  scale, 
touching  tlie  convolutions  of  wire  until  the  galvanometer  reverses  its  deflection. 

Multiples  of  .50  are  read  on  the  horizontal  scale  and  fractions  of  a  turn  on 
the  drum  at  the  right.  The  tabular  number  corresponding  to  this  number,  as 
found  in  the  table  on  the  lid  of  the  olunmeter,  when  nudtiplied  by  10  or  1(M». 
depending  on  whether  tlie  plug  is  at  10  or  KM),  will  give  the  correct  resistance. 

For  example,  if  the  balance  is  found  between  convolutions  Nos.  150  and 
200  on  the  horizontal  scale  and  the  drum  scale  reads  46,  the  exact  reading  is 
196.  Referring  to  the  table,  the  number  corresponding  to  this  is  0.2438,  and 
the  resistance,  if  the  plug  is  inserted  at  10,  will  be  2.438  ohms;  or,  if  the  plug 
is  inserted  at  100,  will  be  24.38  ohms. 


(153) 


54  Signal  Corps  Manual  No.  3. — Chapter  4. 

A  telephone  receiver  may  be  used  in  place  of  the  galvanometer  in  the  ohm- 
meter  by  disconnecting  one  of  the  cords  from  the  post  marked  "  Tel."  and 
connecting  the  receiver  to  those  posts. 

The  portable  galvanometer  may  be  used  in  the  place  of  the  galvanometer 
in  the  ohmmeter  by  proceeding  as  for  the  receiver.  In  this  case  it  would  be 
advisable,  however,  to  make  use  of  the  galvanometer  with  shunt. 

The  method  of  measuring  conductor  resistance  of  a  cable  is  shown  in  figure 
4-42.  The  copper  resistance  is  tested  in  pairs  and  should  not  vary  to  any 
great  extent  (in  very  large  cables  the  outer  layers  will  be  a  few  per  cent 
higher  in  resistance  than  the  inner  layers).  The  resistance  per  stretch  is 
ordinarily  determined  by  dividing  the  loop  reading  by  2.  The  resistance  per 
mile  is  determined  by  dividing  the  total  resistance  per  stretch  by  the  number 
of  miles  in  the  stretch. 

Methods  of  testing  to  locate  faults  in  cables  are  described  in  detail,  chapter  9. 

POINTS   FOK   THE   TESTER. 

1.  Never  open  a  paper  cable  on  a  damp,  misty,  or  rainy  day,  whether  under 
cover  or  not. 

2.  Never  pronounce  a  cable  bad  until  you  are  satisfied  that  all  ends  are 
absolutely  clear  and  dry. 

3.  Never  test  any  kind  of  cable  on  a  damp  day  if  it  can  be  avoided. 

4.  Use  the  service-testing  battery  for  insulation  only,  thus  saving  it  against 
possible  short  circuit  or  heavy  drain. 

5.  Get  thoroughly  acquainted  with  the  instruments  before  starting  the  test 
and  mark  all  the  adjustments,  so  that  little  time  need  be  wasted  in  setting  up. 

6.  Remember  that  accurate  readings  never  are  possible  under  moist  con- 
ditions, and  instruments  and  leads  should  be  as  dry  as  practicable. 

7.  The  micrometer  caliper  should  be  used  to  determine  exact  diameter  of 
the  conductor. 

8.  All  data  concerning  the  cable  should  be  recorded  before  taking  down  the 
instruments,  luMug  sure  that  data  is  complete  for  each  conductor. 

The  following  tables  contain  data  wliich  may  be  of  value  to  the  tester: 


(1R4) 


Cable  and  Cable  Systems. — Chapter  4. 
Tabic  uf  dihicnuiona,  icciyfit,  and  Icnijtk  of  ijurc  copijer  ivire. 


55 


Size, 
Brown  & 
Sharpe. 

Diameter, 
mil.s. 

Circular, 
mils.  (if-).    1 
mil. =.001  in. 

Pounds 

per  1 ,0(K) 

feet. 

I'ouml.s  per 
mile. 

Feet  per 
pound. 

0000 

460.000 

211600.00 

639.33 

3,375.7 

1.56- 

000 

409.640 

167805.00 

507.01 

2,677.0 

1.97 

00 

364.800 

133079. 40 

402.09 

2,123.0 

2.49 

0 

324.  860 

10.5538.00 

318.86 

1,683.6 

3.14 

1 

2S9. 300 

83694.  20 

252. 88 

1,335.2 

3.95 

2 

257. 630 

66373.00 

200.  54 

1,058.8 

4.99 

3 

229.  420 

52034.  (K) 

1,59. 03 

839.68 

6.29 

4 

204.310 

41742.  (K) 

126. 12 

()05. 91 

'  7,93 

5 

181. 940 

33102. 00 

100.01 

528. 05 

10.00 

6 

162.020 

262.50. 50 

79. 32 

418.81 

12.61 

7 

144.  280 

20816.  00 

62.90 

332.11 

1,5. 90 

8 

128.  490 

16.509. 00 

49.88 

2t)3. 37 

20. 05 

9 

114.430 

13094.00 

39.  .56 

208.  88 

2.5.  28 

10 

101. 890 

10.381.00 

31.37 

16.5. 63 

31.38 

n 

90.742 

8234. 00 

24.88 

131. 37 

40.  20 

12 

80.808 

6529. 90 

19.73 

101. 18 

.50.  69 

13 

71.961 

5178.  40 

1,5.  65 

82. 632 

6:?.  91 

14 

64.048 

410().  70 

12.44 

65. 674 

80.38 

15 

57.068 

3256.  7 

9.84 

51.956 

101. 63 

16 

50.820 

2582. 9 

7.81 

41.237 

128. 14 

17 

45.  257 

2048.  2 

6.19 

32.683 

161. 59 

18 

40. 303 

1624. 3 

4.91 

2,5.925 

203.76 

11) 

35. 876 

1287. 1 

3.  88 

20. 507 

2.57.  47 

20 

31. 961 

1021.5 

3.09 

16.315 

324.00 

21 

28.  462 

810. 10 

2.  45 

12. 936 

408.56 

22 

25.347 

642.70 

1.94 

10. 243 

515. 15 

23 

22. 571 

509.  45 

1.54 

8.1312 

649.66 

24 

20.100 

404.  01 

1.22 

6.4416 

819.  21 

25 

17.900 

320.  40 

.97 

.5. 1216 

1,032.% 

•   26 

15. 940 

254.  01 

.  77 

4.0656 

1,302.61 

27 

14. 195 

201.  50 

.61 

3. 2208 

1.642.  ,55 

28 

12.641 

159.  79 

.48 

2. 5344 

2,071.22 

29 

11.257 

126.  72 

.38 

2.0064 

2.611.82 

30 

10.025 

100.5 

.30 

1.  ,5840 

3.293.97 

31 

8.928 

79.71 

.24 

1.2672 

4,152.22 

32 

7.950 

63.20 

.19 

1.0032 

5, 236. 66 

33 

7.080 

50.13 

.15 

.7920 

6,602.71 

34 

6.304 

39.74 

.12 

.6336 

8., 328. 30 

35 

5.614 

31.52 

.10 

.  52,80 

10,501.35 

36 

5.000 

25.00 

.08 

.4224 

13,238.83 

37 

4.453 

19.83 

.06 

.3168 

16,691.06 

3S 

3.965 

15.72 

.05 

.2640 

20.851.65 

39 

3.531 

12.47 

.04 

.2112 

26.  ,302. 23 

40 

3.144 

9.89 

.03 

.1584 

33.175.94 

46581°— 17- 


-11 


(155) 


56 


Signal  Corps  Manual  No.  3. — Chapter  4. 
Table  of  resistances  of  pure  copper  wire  at  75°  F. 


Size, 
Brown  & 
Sharpe. 

Ohms  per 
1,000  feel. 

Ohms  per 
mile. 

Ohms  per  pound. 

Feet  per  ohm. 

0000 

0. 04906 

0. 25903 

0. 000076736 

20, 383. 0 

000 

.06186 

.  32664 

.  00012039 

16.165.0 

00 

.07801 

.41187 

.  00019423 

12,820.0 

0 

.09838 

.  51937 

.  00038.500 

10, 166. 0 

1 

.  12404 

.65490 

.  00048994 

8, 062. 3 

2 

.  15640 

. 82582 

.  00078045 

6, 393.  7 

3 

.  19723 

1.0414 

.  0012406 

5. 070. 2 

4 

.24869 

1.3131 

.  0019721 

4,021.0 

5 

.  31361 

1.6558 

.  0031361 

3,188.7 

6 

.  39546 

2.0881 

.  0049868 

2, 528.  7 

7 

.  49871 

2.  6331 

.  0079294 

2, 005. 2 

8 

.  62881 

3. 3201 

.  012608 

1,590.3 

9 

.  79281 

4. 1860 

.  020042 

1,261.3 

10 

1.0000 

5. 2800 

.  031380 

1.000.0 

11 

1. 2607 

6.  6568 

.  050682 

793. 18 

12 

1. 5898 

8. 3940 

.  080585 

629. 02 

13 

2. 0047 

10. 585 

.  12841 

498.  83 

14 

2. 5278 

13.347 

.  20322 

395. 60 

15 

3.1150 

16.  477 

.  31658 

321.02 

1(> 

4.0191 

21.221 

.  51501 

218.81 

17 

5. 0683 

26.  761 

.81900 

197.30 

18 

6.39U 

33.  745 

1.3023 

!.-)6.47 

19 

8. 0651 

42. 5S5 

2. 0759 

123. 99 

20 

10. 163 

.53. 658 

3. 2926 

98.  401 

21 

12.815 

67.  660 

5. 2355 

78.  067 

22 

16. 152 

85. 283 

8. 3208 

61.911 

23 

20. 377 

107.  59 

13. 238 

49. 087 

24 

25. 695 

135.  67 

21.  050 

38.918 

25 

32.  400 

171.07 

33.  466 

30.  864 

26 

40. 868 

215.  79 

35. 235 

24.  46^ 

27 

51. 519 

272. 02 

84.  644 

19.410 

28 

64.  966 

343. 02 

134. 56 

15.  393 

29 

81.921 

432.  54 

213.% 

12. 207 

30 

103.  30 

545. 39 

340.25 

9.  6812 

31 

127.27 

671.99 

528.  45 

7.  8573 

32 

164. 26 

867. 27 

860. 33 

6.0880 

33 

207.  08 

1,093.4 

1,367.3 

4.  8290 

34 

261. 23 

1,379.3 

2,17.5.5 

3.  8281 

35 

329. 35 

1,738.9 

3. 468. 5 

3.0363 

36 

415.24 

2, 192. 5 

5, 497.  4 

2. 4082 

37 

523.  76 

2,  765. 5 

8, 742. 1 

1.9093 

38 

660.  37 

3, 486.  7 

13, 772. 

1.5143 

39 

832.48 

4, 395. 5 

21.896. 

1.2012 

40 

1,049.7 

5,542.1 

34, 823. 

.9527 

In  roducinjr  I  lie  iiisiilation  resi.'^tance  of  Okoiiito,  Hnbirshaw,  or  Bishop  c-oni- 
pouiids  to  60°  F.,  the  total  (Urt'creiice  botwi'i'ii  \hv  toiniKTature  of  ob.sorvation 
and  the  standjird  temperature,  00°,  will  he  deteriuiiied  and  the  proper  coeHicient 
will  he  found  hy  referrinj;  to  the  tahle.  For  example,  if  the  temperature  were 
75°,  the  difference  of  temperature,  15°,  would  call  for  a  coellicient  of  1.470,  hy 
which  tlie  insulation  resistance,  as  calculated,  will  be  multiplied  to  determine 
the  correct  value  at  60°  F. 


(ir.6) 


Cable  and  Cable  Systems. — Chapter  4. 


57 


Temperature  of  cocfflcicnts  for  the  reduction  of  insulation  resistaiice  to  60°  F. 

OKONITE,  HABIRSHAW,  AND  BISHOP  COMPOUNDS. 


Diflerence 

1 

Diflerence 

Difference 

of  tempera- 

Coellicient. 

of  tempera- 

Coeflacient. 

oftempera^ 

Coefficient. 

ture. 

ture. 

tare. 

"F. 

'F. 

"F. 

1 

1.026 

18 

1.587 

35 

2.456 

2 

1.053 

19 

1.629 

36 

2.520 

3 

^       1.080 

20 

1.671 

37 

2.586 

4 

1.108 

21 

1.715 

38 

2.653 

5 

1. 137    ! 

22 

1.759 

39 

2.722 

6 

1.167 

23 

1.805 

40 

2.796 

7 

1. 197 

24 

1.852 

41 

2.865 

8 

1.228    I 

25 

1.900 

42 

2.940 

9 

1.260 

26 

1.949 

43 

3.016 

10 

1.293 

27 

2.000 

44 

3.091 

11 

1.326 

■     28 

2.0.52 

45 

3.175 

12 

1.361 

29 

2.105 

46 

3.  258 

v^ 

1.396 

30 

2.160 

47 

3.342 

14 

1.433 

31 

2.216 

48 

3.429 

15 

1.470 

32 

2.274 

49 

3.518 

Iti 

1.508 

33 

2.333 

50 

3. 610 

17 

1.547 

34 

2.394 

To  correct  insulation  resistance  for  temperature  wliere  the  cables  are  made 
up  of  Safety,  Kerite,  or  Standard  underground  rul)ber  compounds,  reference 
should  be  made  to  one  of  the  following  tables  for  the  temperature  coefficient 
at  the  ob.served  temperature.  The  correct  resistance  is  obtained  by  multiply- 
ing the  calculated  resistance  by  the  coefficient  found  in  the  table  for  that 
compound  opposite  the  observed  temperature. 

SAFETY  COMPOUND. 


Tempera- 
ture. 

Coefficient. 

Tempera- 
ture. 

Coefficient. 

Tempera- 
ture. 

Coefficient. 

"F. 

°F. 

"F. 

20 

0.4399 

47 

0. 7386 

74 

1.4407 

21 

.4472 

48 

.7551 

75 

1.4811 

22 

.4.547 

49 

.7721 

76 

l.,5228 

23 

.4625 

50 

.7897 

77 

1.5647 

24 

.4705 

51 

.8078 

78 

1.6110 

25 

.4787 

52 

.8265 

79 

1.6728 

26 

.  4869 

53 

.8458 

80 

1. 7056 

27 

.4959 

54 

.8658 

81 

1. 7556 

28 

.5049 

55 

.8864 

82 

1.8073 

29 

.5141 

56 

.9076 

83 

1.8610 

30 

..5237 

57 

.9296 

84 

1.9167 

31 

.5335 

58 

.9523 

85 

1.9744 

32 

.  .5437 

59 

.  9758 

86 

2. 0343 

33 

..5542 

60 

1.0000 

87 

2.0964 

34 

.5648 

61 

1.0251 

88 

2.1609 

35 

.5759 

62 

1.0,510 

89 

2.2278 

36 

..5873 

63 

1.0777 

90 

2. 2973 

37 

.5990 

64 

1.1054 

91 

2.3694 

38 

.0112 

65 

1. 1340 

92 

2.4443 

39 

.6236 

66 

1.1036 

93 

2.5223 

40 

.0351 

67 

1.1943 

94 

2.6028 

41 

.6498 

68 

1.2260 

95 

2.6808 

42 

.6635 

69 

1.2587 

96 

2. 7740 

43 

.  6776 

70 

1.2927 

97 

2.8646 

44 

.6921 

71 

1. 3278 

98 

2.9587 

45 

.7071 

72 

1..3641 

99 

3.0566 

46 

.7226 

73 

1.4017 

100 

3.1584 

(157) 


58 


Signal  Corps  Manual  No.  3. — Chapter  4. 


Temperature  of  coefficients  for  the  reduction  of  insulation  resistance  to  60°  F. 

Continued. 

KERITE  COMPOUND. 


Temper- 
ature. 

Coefficient. 

Temper- 
ature. 

Coefficient. 

Temper- 
ature. 

Coefficient. 

°  F. 

°  F. 

°  F. 

20 

0. 2706 

47 

0.5187 

74 

2.6023 

21 

.2725 

48 

.5413 

75 

2.8410 

22 

.2747 

49 

.5655 

76 

3.0469 

23 

.2774 

50 

.5917 

77 

3.3035 

24 

.2804 

51 

.6199 

78 

3. 5865 

25 

.2839 

52 

.6503 

79 

3. 8988 

26 

.2877 

53 

.  6831 

80 

4.2438 

27 

.2921 

54 

.  7184 

81 

4.6256 

28 

.  2968 

55 

.7566 

82 

5. 0483 

29 

.3020 

56 

.7979 

83 

5. 5169 

30 

.3078 

57 

.  8426 

84 

6. 0371 

31 

.3141 

58 

.8909 

85 

6.6149 

32 

.3209 

59 

.9433 

86 

7. 2577 

33 

.32,S3 

60 

1.0(K)0 

87 

7.9734 

34 

.3363 

61 

1.0616 

88 

8.  7713 

35 

.3449 

62 

1.1281 

89 

9.6617 

36 

.  3543 

63 

1.2010 

90 

10. 6566 

37 

.3644 

64 

1.2S0() 

91 

11.7695 

38 

. 3752 • 

65 

1.3660 

92 

13.01.58 

39 

.  3869 

66 

1.4597 

93 

14.4130 

40 

.3995 

67 

1..5618 

94 

15.9814 

41 

.4131 

68 

1.6772 

95 

17.  7438 

42 

.4276 

69 

1.7952 

96 

19.  7265 

43 

.  44.33 

70 

1.9285 

97 

21. 9598 

44 

.4601 

71 

2.0744 

98 

24. 4782 

45 

.4782 

72 

2. 2343 

99 

27.3215 

46 

.4977 

73 

2. 4097 

100 

30.5353 

STANDARD  UNDERGROUND  CO.'S  RUBBER  "D.' 


Temper- 
ature. 

Coefficient. 

Temper- 
ature. 

Coefficient . 

Temper- 
ature. 

Coefficient. 

°  F. 

°  F. 

°  F. 

20 

0. 5536 

47 

0.8051 

74 

1.2970 

21 

.  5603 

48 

.8179 

75 

1.3227 

22 

.  .5672 

49 

.  8311 

76 

1.3491 

23 

.5742 

,50 

.8446 

77 

1.3762 

24 

.5814 

51 

.  .'v5S4 

78 

1.4041 

25 

.  5888 

52 

.8726 

79 

1 .  432.S 

26 

.  .5964 

.53 

.8872 

80 

1.4622 

27 

.  6041 

54 

.9021 

81 

1.4924 

28 

.6120 

55 

.9174 

82 

1..5235 

29 

.6201 

56 

.9.331 

83 

1.. 5.5.54 

30 

.  6284 

57 

.  9492 

84 

1 . 5SK3 

31 

.  6369 

5X 

.  9()57 

.85 

1 .  6220 

32 

.  64.56 

,59 

.  9S26 

.Sti 

1 .  6568 

33 

.  6,54() 

60 

I.IXHX) 

.S7 

1.6!t24 

34 

.  6626 

61 

I.()I7.S 

8K 

1.7291 

35 

.6731 

62 

1.0.%1 

.S!l 

l.76t;!i 

36 

.6827 

63 

1.0549 

90 

1.S0.57 

37 

.  6925 

64 

1.0741 

91 

1.84.57 

38 

.  7026 

6.5 

1 .  093!) 

92 

1 . SS67 

39 

.7129 

66 

1.1141 

93 

1 . 9290 

40 

.  7234 

(u 

1.1.349 

94 

1.9725 

41 

.  7343 

68 

1.1.563 

!»5 

2.0173 

42 

.  7454 

69 

1 .  1 782 

9() 

2. 06:i:t 

43 

.7,567 

70 

1 . 2(K)7 

97 

2. 1107 

44 

.7684 

71 

1.22.3il 

9S 

2.1.595 

45 

.  7803 

72 

1.2476 

!t9 

2.  20!)8 

46 

.  7925 

73 

1.2720 

1(K) 

2.  2615 

(158) 


Cable  and  Cable  Systems. — Chapter  4. 


.59 


The  re.sistance  of  copper  incroasos  witli  tlic  increase  of  temperature.  In  order 
to  reduce  copper  resistances  at  any  temperature  between  0°  and  120°  V.  to  W 
F.,  tlie  followinji  table  has  been  calculated,  in  which  6  is  the  factor  by  which 
the  resistance  at  the  observed  teni])t'rature  should  he  multiplied  to  reduce  it 
to  60°  F. : 

Reduction  of  copijcr  rcftixtfnirc  to  (;0°  F. 


Temper- 

5 

Temper- 

S 

Temper- 

J 

ature. 

ature. 

ature. 

"  F. 

°  F. 

"  J^. 

0 

1.  l.iSS 

41 

1.0443 

82 

0.9,529 

1 

1. 1,509 

42 

1. 0419 

83 

.  9.508 

2 

1.1480 

43 

1.  0395 

84 

.9488 

■i 

1.  14,51 

44 

1. 0371 

85 

.9468 

4 

1.  1422 

45 

1.  0347 

86 

.9448 

o 

1.  1393 

46 

1.  0323 

87 

.9428 

C 

1.  1364 

47 

1. 0300 

88 

.9408 

7 

1.  1336 

48 

1. 0276 

89 

.9388 

8 

1.  1308 

49 

1. 0252 

90 

.9368 

9 

1.  1280 

,50 

1.0229 

91 

.9348 

10 

1.  12,52 

51 

1.0206 

92 

.9328 

11 

1.  1224 

52 

1. 0182 

93 

.  9308 

12 

1.1196 

.53 

1. 0159 

94 

.9288 

13 

1.1168 

.54 

1. 0136 

95 

.9269 

14 

1.1141 

55 

1.0113 

96 

.  92.50 

l-> 

1.1113 

56 

1.0090 

97 

.92:J1 

16 

1.11)86 

57 

1.0068 

98 

.9211 

17 

1.  1U.59 

58 

1.0045 

99 

.  9192 

18 

1.  1032 

,59 

1.0023 

100 

.  9173 

19 

1.  100,5 

60 

1.0000 

101 

.91,54 

20 

1.0978 

61 

.9978 

102 

.  9135 

21 

1.  09,52 

62 

.  99,56 

103 

.9116 

22 

1.  0925 

63 

.9933 

104 

.9097 

23 

1.  0899 

64 

.9911 

105 

.9097 

24 

1.  0S73 

65 

.9889 

106 

.9060 

2,5 

1.  0846 

66 

.9867 

107 

.9041 

26 

1. 0820 

67 

.9846 

108 

.9022 

27 

1. 0794 

68 

.9824 

109 

.9004 

28 

1. 0769 

69 

.9802 

110 

.8986 

29 

1. 0743 

70 

.9781 

111 

.8968 

30 

1.0717 

71 

.9759 

112 

.8949 

31 

1.0692 

72 

.9738 

113 

.8931 

32 

1.0667 

73 

.9717 

114 

.8913 

33 

1.0641 

74 

.9695 

115 

.8895 

34 

1. 0616 

75 

.9674 

116 

.8877 

35 

1. 0,591 

76 

.9653 

117 

.8859 

36 

1. 0,566 

77 

.9632 

118 

.8841 

37 

1.  0,542 

78 

.9611 

119 

.8824 

38 

1. 0517 

79 

.  9.591 

120 

.8806 

39 

1. 0492 

80 

.9570 

40 

1.0468 

81 

.9549 

A  general  formula  for  reducing  copper  resistance  at  any  observed  tempera- 
ture (T)  to  60°  F.  is  given  by  the  following: 


5= 


1.063 


l+,00225  (T-32) 


(15!» 


60 


Signal  Corps  Manual  No.  3. — Chapter  4. 

Wire  table,  standard  annealed  copper. 
I  American  wire  gauge  (B.  &  S.).] 


Cross  section. 

Ohms  per  1,000  feet. 

Gauge 
No. 

Diameter 
ill  mils. 

Circular  mils. 

Square  inches. 

0°C. 
(=32°  F.). 

15°  C. 
(=59°  F.). 

20°  C. 

(=68°  F.). 

0000 

000 

00 

460.0 
409.6 
364.8 

211  600. 

167  800. 
133  100. 

0. 1662 
.1318 
.1045 

0.045  14 
.  056  93 
.071  78 

0.048  04 
.060  58 
. 076  39 

0. 049  01 
.061  80 
. 077  93 

0 

1 
2 

324.9 
289.3 
257.6 

105  500. 
83  690. 
66  370. 

.082  89 
.065  73 
.052  13 

.090  .'-,2 

.1141 

.1439 

.096  33 

.1215 

.1532 

.  098  27 

.1239 

.1563 

3 

4 
5 

229.4 
204.3 
181.9 

52  640. 
41  740. 
33  100. 

.041  34          ' 

.032  78 

.  026  00         ; 

.1815 
.2288 
.2886 

.1931 
.  2436 
.3071 

.1970 
.2485 
.3133 

6 

7 
8 

162.0 
144.3 
128.5 

26  250. 
20  820. 
16  510. 

.020  62 
.  016  35 
.012  97 

.3639 
.4589 
.5786 

.3872 
.4883 
.6158 

.3951 
.  4982 
.6282 

9 
10 
11 

114.4 
101.9 
90.74 

13  090. 

10  380. 

8234. 

.  010  28 
.008  WS 
. 006  467 

.7296 
.9200 
1.160 

.7765 
.9792 
1.235 

.7921 
.9989 
1.260 

12 
13 

14 

80.81 
71.96 
64.08 

6530. 
5178. 
4107. 

.005  129 
.004  067 
.003  225 

1.463 
1.845 
2.326 

1.557 
1.96:} 
2. 475 

1.588 
2.003 
2.525 

15 
16 
17 

57.07 
50.82 
45.26 

3257. 
2583. 
2048. 

. 002  558 
. 002  028 
.001  609 

2.933 
3. 699 
4.664 

3.121 
3.936 
4.963 

3.184 
4.015 
5.064 

18 
19 
20 

40.30 
35. 89 
31.96 

1624. 

1288. 
1022. 

.001  276 
.001  012 
. 000  802  3 

5.881 
7.416 
9.352 

6.259« 
7.892 
9.953 

C.385 
8.051 
10.15 

21 
22 
23 

28.46 
25.35 
22. 5/ 

810.1 
642.4 
509.5 

. 000  636  3 
. 000  504  6 
. 000  400  2 

11.79 
14.87 
18.75 

12.55 
15.82 
19. 95 

12.80 
16.14 
20.36 

24 
25 
26 

20.10 
17.90 
15.94 

404.0 
320.4 
254.1 

. 000  317  3 
.000  251  7 
. 000  199  6 

23.64 
29.  81 
37.  ,59 

25.16 
31.  73 
40.01 

25.67 
32. 37 
40.82 

27 
28 
29 

14.20 
12.64 
11.26 

201.5 
159.8 
126.7 

.  000  158  3 
.  000  125  5 
.  000  099  53 

47.40 
59.  77 
75.37 

50.45 
()3.61 
80.22 

51.46 
64.90 

81.84 

30 
31 
32 

10.03 

8.928 
7. 950 

100.5 
79.70 
63.21 

.  000  078  94 
. 000  062  60 
. 000  049  64 

95.05 
119.8 
151.1 

101.2 
127.6 
160.8 

103.2 
130.1 
164.1 

33 
34 
35 

7.080 
6.305 
5.615 

50.13 
39.75 
31.52 

.  000  039  37 
.000  031  22 
.  000  024  76 

190.6 
240.3 
303.0 

202.8 
255.7 
322. 5 

206.9 
260. 9 
329. 0 

36 
37 
38 

5.000 
4.453 
3.965 

25.00 
19.83 
15.72 

.  000  019  64 
.000  015  57 
.  000  012  35 

382.1 
481.8 
607. 5 

406.6 
512.  S 
646.6 

414.8 
523.1 
659. 6 

39 
40 

3.531 
3.145 

12.47 

9.888 

.  000  009  793 
.000  007  766 

766. 1 
966. 1 

815.4 
1028. 

831.  8 
1049. 

(160) 


Cable  and  Cable  Systems. — Chapter  4. 

Wire  table,  standard  annealed  copper — Continued. 
[American   wire   gauge   (B.    &   S.).] 


61 


Gauge 
No. 

Diameter 
in  mils. 

Cross 

section. 

Ohms  per  1,000  feet. 

Circular  mils. 

Square  inches. 

25' C. 
(  =  77°  F.). 

50°  C. 
(  =  122°  F.). 

75°  C. 

(=167°  F.). 

(XX)0 
(XK) 
00 

4(iO.  0 
409.  (1 
3(14. 8 

211  im. 
107  800. 
133  100. 

0.1602 
.1318 
.1045 

0. 049  98 
.Oti3  03 
.079  47 

0.054  82 
.069  12 
.087  16 

0.059  65 
.075  22 
.094  8.5 

0 
1 

2 

324.9 

289.3 
257.  (i 

105  500. 
8.3  090. 
0(i  370. 

.  082  89 
.005  73 
.052  13 

.1002 
.1204 
.1594 

.1099 
.  1386 
.1748 

.1190 

.  l.")(l>S 
.1902 

3 
4 

5 

229.4 
204.3 
181.9 

52  040. 
41  740. 
33  100. 

.041  34 
.  032. 78 
.026  00 

.2009 
.2534 
.3195 

.2204 
.  2779 
.3504 

.2398 
.3024 
.,3813 

0 
7 

8 

1(12. 0 
144.3 
128. 5 

2(;  2,50. 
20  820. 
10  510. 

.  020  62 
.016  35 
.012  97 

.4029 
.5080 
.6406 

.4418 
.  5572 
.  7025 

.4808 
.6004 
.7645 

9 
10 
11 

114.4 
11)1.9 
90.74 

13  090. 

10  3,S0. 

8234. 

.010  28 
.008  155 
.006  467 

.8078 
1.019 
1.284 

.8800 
1.117 
1.409 

.9641 
1.216 
1.  ,5.33 

12 
13 
14 

80.81 
71.  9Ci 

04.08 

5178. 
4107. 

.005  129 
. 004  007 
. 003  225 

1.620 
2.042 
2.576 

1.770 
2.240 

2.824 

1.933 

2.438 
3.074 

15 
10 
17 

57.07 
50.  82 
45. 26 

3257. 
2.583. 
2048. 

. 002  558 
. 002  028 
.001  009 

3.248 
4.095 
5.164 

3.502 
4.491 
5. 003 

3.876 
4.887 
6. 162 

18 
19 
20 

40.  .30 
35.  s9 
31.90 

1624. 

1288. 
1022. 

.001  270 
.001  012 
.000  802  3 

6.512 
8. 210 
10.35 

7.141 
9.004 
11.30 

7.771 
9.799 
12.36 

21 
23 

28. 40 
2.5. 35 
22.57 

810.1 
642.4 
509.5 

.000  636  3 
. 000  504  6 
. 000  400  2 

13.06 
16. 46 
20.76 

14.32 

IS.  06 
22.77 

15.58 
19.  (a 

24.78 

24 
25 
26 

20.10 
17.90 
15.94 

404.0 
320. 4 
254.1 

.0<X)  317  3 
.0(H)  251  7 
.000  199  6 

26.18 
33.01 
41.62 

28.71 
30. 20 
45.05 

31.24 
,39.39 
49.68 

27 
28 
29 

14.20 
12.04 
11.26 

201.5 
159.8 
126.7 

.000  158  3 
. 000  125  5 
.000  099  53 

52.48 
66.18 
83.46 

57.56 
72.59 
91.53 

62.64 
78.98 
99.60 

30 
31 
32 

10.03 
8.928 
7.950 

100.5 
79.70 
63.21 

.000  078  94 
. 000  062  60 
.  000  049  64 

105.2 
132.7 
167.3 

115.4 
145.5 
183.5 

125. 6 
158.4 
199.7 

33 
34 
35 

7.080 
0. 305 
5. 015 

50.13 
39.75 
31.52 

. 000  039  37 
.(K)0  031  22 
.000  024  70 

211.0 
266. 1 
335.5 

231.4 

291.8 
367.9 

251.8 
317.5 
400.4 

3() 
37 
38 

5.000 
4. 4.^)3 
3. 9ti5 

25.00 
19.83 
15.72 

.000  019  04 
.000  015  57 
.000  012  35 

423.0 
5,33.5 
672.7 

464.0 
5S5.1 
737.7 

504.9 
636.7 
802.8 

39 
40 

3.  531 
3.  145 

12.47 

9.888 

.  000  009  793 

.  (H»0  007  700 

848.2 
1070. 

930.2 
1173. 

1012.0 

1270. 

(161) 


62 


Signal  Corps  Manual  No.  3. — Chapter  4. 
Wire  table,  standard  annealed  copper. 

[American  wire  gauge  (B.  &  S.)I 


Feet  per  ohm. 

Gauge 
No. 

Diam- 
eter in 
mils. 

Pounds 

per  1,000 

feet. 

Feet  per 
pound. 

0°C. 
(=32° 

F.). 

15°  C. 

(=59° 

F.). 

20°  C. 

(=68° 
F.). 

25°  r. 

(=77° 
F.). 

50°  0. 

(=122° 

F.). 

75°  r. 
(=167° 

F.). 

0000 

000 

00 

400.0 
109.6 
304.8 

040.5 
507. 9 
402.8 

1.501 

1.  90S 

2.  482 

22  150. 
17  570. 
13  930. 

20  810. 
10  510. 
13  090. 

20  400. 
10  ISO. 
12  830. 

20  010. 
15  870. 
12  580. 

18  240. 
14  470. 
11  470. 

10  700. 
13  290. 
10  540. 

0 
1 
2 

324.9 
289.3 
257.6 

319.5 
a53.3 
200.9 

3.130 
3.947 
4.977 

11  050. 
875 1. 
6948. 

10  380. 
8233. 
0529. 

10  ISO. 
8070. 
0400. 

9979. 
7913. 
6270. 

9098. 
7215. 
5722. 

8.361. 
6630. 
5258. 

3 

4 
5 

229.4 
204.3 
181.9 

159. 3 
126.4 
100.2 

6. 276 
7.914 
9.980 

5510. 
4370. 
3465. 

5178. 
4100. 
3250. 

5075. 
4025. 
3192. 

4977. 
.3947. 
3130. 

4538. 
3599. 
2854. 

4170. 
3307. 
2022. 

6 

7 
8 

162.0 
114.3 
128.5 

79.40 
63. 02 
49.98 

12.58 
15.  S7 
20.01 

2748. 
2179. 
172S. 

2582. 
2048. 
1024. 

2531. 
2007. 
1592. 

2482. 
1968. 
1561. 

2263. 
1795. 
1423. 

2080. 
1049. 
1308. 

9 
10 
11 

114.4 
101.9 
90.74 

39.63 
31.43 
24.92 

25. 23 
31. 82 
40.12 

1371. 
1087. 
802.0 

1288. 
1021. 
810.0 

1202. 
1001. 
794.0 

1238. 
981.  8 
778.5 

1129. 
895. 1 
709.9 

1037. 
822. 6 
652.4 

12 
13 
14 

80.81 
71. 90 
04. 08 

19.77 
15. 68 
12.43 

50.59 
63. 80 
80.44 

083.6 
542. 0 
429.9 

642. 3 
.509.4 
404.0 

629.6 
499.3 
396.0 

617.4 
489. 0 
388. 3 

.563.0 
440.4 
.354.  0 

517. 3 
410.3 

325. 4 

15 
16 
17 

57.07 
50.82 
45. 26 

9. 858 
7. 818 
6.200 

101.4 
127.9 
161.3 

340.9 
270.4 
214.4 

320.  4 
254.  1 
201.  5 

314.0 
249.0 
197.5 

307.9 
244.2 
193.  7 

280.  8 
222.7 
170.0 

258. 0 
201. 0 
162. 3 

18 
19 
20 

40.30 
35.89 
31.96 

4.917 
3.899 
3.092 

203. 4 
2.50.5 
323. 4 

170.0 

134. 8 

100. 9 

159.  8 
120.  7 
100.5 

150.  0 
124.2 
98.  49 

153.0 
121.8 
90. 59 

140.0 
111.1 

88.07 

128.  7 
102. 0 
80.93 

21 
22 
23 

28. 46 
2.5. 35 
22.57 

2.452 
1.945 
1..542 

407.8 
514.2 
048. 4 

84.81 
67.  25 
53. 34 

79.09 
03.  20 
50. 12 

78.11 
01.95 
49.12 

7().  00 
00.  74 
48.17 

09. 84 
.55.39 
43. 92 

04.  IS 
50. 90 
40. 36 

21" 

2r> 

2(i 

20.10 
17.90 
15. 94 

1.223 
0.  9699 
.  7692 

817.  7 
1031. 
1300. 

42.  .30 
33. 54 
26.  60 

39.74 
31.52 
25.00 

38.96 
30.90 
24.50 

38.20 
30.  30 
24.02 

34.  83 

27. 02 

.  21.91 

32.01 
25. 39 
20. 13 

27 

28 
29 

14.20 
12.  (;4 
11.20 

.6100 
.  4837 
.38:^6 

1039. 
2007. 
2007. 

21.10 
16.  73 
13.  27 

19. 82 
15.  72 
12.47 

19.  43 
15.41 
12.22 

19. 05 
15.11 
11.98 

17.37 
13.  78 
10.93 

15. 90 
12. 66 
10.04 

30 
31 
32 

10.03 
8.928 
7.950 

.3042 
.2413 
.  1913 

3287. 
4145. 
5227. 

10.52 
8.344 
6.617 

9.886 
7.840 
6.218 

9. 691 
7.  085 
0.094 

9.503 
7.530 
5.970 

8. 605 
6.871 
5.449 

7.962 
6.314 
5.008 

33 
34 

35 

7.080 
6.305 
5. 615 

.1517 
.1203 
.095  42 

6591. 

8310. 

10  480. 

5.  247 
4. 161 
3.  .300 

4.931 
3.910 
3. 101 

4. 833 
3.  833 
.3.040 

4.739 
3.  759 
2. 981 

4.322 
3.427 
2.718 

3.971 
3.149 
2.497 

.10 
37 
38 

5.000 
4.  453 
3. 90.5 

.075  68 
.0()0  0I 
.047  .59 

13  210. 
16  600. 
21  010. 

2.617 
2. 075 
1. 040 

2. 459 
1.950 

1.547 

2.410 
1.912 
1.516 

2. 304 
1.874 
1.487 

2. 155 
1.709 
1.  .356 

1.981 
1. 571 
1. 246 

39 
40 

3.531 
3.145 

.a37  74 
.029  93 

20  500. 
33  410. 

1.305 
1.035 

1.220 
0. 9727 

1.202 
0. 9534 

1.179 
0. 9349 

1.075 
0. 8525 

0.9878 
.7834 

(162) 


Cable  and  Cable  Systems. — Chapter  4. 


03 


Wire  table,  Htnndard  finiicfileil  topper. 
[Ainerican  wire  ^auge  (B.  A:  S.).) 


Gauge 
No. 

Diameter 
in  mils. 

1 
Ohms  per  pound.                                        ] 

0°C.  (=32"?.). 

15°  C.  (-59°  F.). 

20°C.  (=68°F.). 

0000 
non 

(10 

460.0 
409.6 
364.  S 

0.000  070  41 
.000  1120 
.()(K)  17S() 

0.000  075  09 
.000  1192 
.(XK)  lS9(i 

0.000  076  52 
.000  1217 
.0(K)  1935 

0 

1 

2 

324.9 
2H9.  3 
257.6 

.  (MH)  2.S30 
.  (MH)  4.500 
.(KM)  71.56 

.000  3015 
jm  4791 
.  000  7622 

.  000  3076 
.0(K)  4S91 
.  (KM)  7778 

3 
4 
5 

229.4 
201.3 
1S1.9 

.001  l.)S 
.(K)l  S09 
.002  S77 

.001  212 
.(K)l  927 
.003  Wil 

.001  237 
.fK)l  966 
.Oa3  127 

6 

7 
S 

162. 0 
144.3 
12S.  5 

.004  574 
.  007  273 
.011  .56 

.004  872 
.007  747 
.012  ,32 

.004  972 
.007  906 
.012  .57 

0 
10 

11 

114.4 
101.9 
iK).  74 

.018  39 
. 029  24 
.046  49 

.019  .59 
.031  15 
.049  .52 

.019  99 
.031  78 
.  0.50  53 

12 
13 
H 

SO.  SI 
71.96 
64.  OS 

. 073  93 
.1176 
.  1S69 

.  078  74 
.  1252 
.1991 

.080  35 
.1278 
.  2032 

1.', 
Ifi 
17 

57.  07 
50.  S2 
4.5.  26 

.2972 
.  4726 
.7514 

.3166 
.  .5033 
.8003 

.  3230 
.51:56 

.su;7 

IS 
19 
20 

40.  30 
35.  S9 
31.96 

1. 195 
1.900 
3.021 

1.273 
2.024 
3.218 

1.299 
2. 065 
3.  2.'s;5 

21 
22 
23 

2S.  46 
25.  35 
22.  57 

4. 803 
7.  t)37 
12.14 

5.116 
8. 135 
12.93 

5.221 
8.302 
13.20 

24 
25 
26 

20.  10 
17.90 
1.').  94 

19.31 
30.70 

48.82 

20. 57 
32.70 
.52.00 

20.99 
33. 37 
,53. 06 

27 
2S 
29 

14.20 
12.  64 
11.26 

77. 63 
123.4 
196.3 

82. 69 
131.5 
209. 1 

84.37 
134.2 
213.3 

30 
31 
32 

10.  03 

S.  928 
7.950 

312.1 
496.3 
789.1 

332.  4 
528. 5 
840.5 

339.2 
539.3 
857.6 

33 

34 
35 

7.080 
6.305 
5.615 

1255. 
1995. 
3172. 

1336. 
2125. 
3379. 

1364. 
2168.  ■ 
3448. 

36 
37 
38 

5.000 
4.453 
3.965 

5044. 

8020. 

12  7.50. 

5372. 

8542. 

13  580. 

5482. 

8717. 

13  860. 

39 
40 

.3.  .531 
3. 145 

20  280. 
32  240. 

21  600. 
34  340. 

22  040. 

35  aio. 

Continued. 


(163) 


64 


Signal  Corps  Manual  No.  3. — Chapter  4. 

Wire  table,  stamlai-d  annealed  eopper — Continued. 
[American  wire  gauge  (B.  &  S.)-] 


Gauge 
No. 

Diameter  in 
mils. 

Ohms  per  poun^. 

25°C.  (=77°  F.). 

50°  C.  (=122°  F.). 

75°  C.  (=167°  F.). 

0000 

(MX) 

0(1 

460.0   • 
409.6    ' 
364.8 

0. 000  078  05 
.000  1241 
.000  1974 

0.000  085  70 
.000  13()3 
.  000  2167 

0. 000  093  34 
.000  148:? 
.000  2360 

0 

1 
2 

324.9 
289.3 
257.6 

.000  3138 
.000  4990 
. 000  7934 

.000  3445 
.000  5478 
.000  8711 

. 000  3753 
.000  5967 
.000  9487 

3 
4 
5 

229.4 
204.3 
181.9 

.001  202 
.  002  OOti 
.CX)3  189 

.001  385 
.002  202 
.003  502 

.001  508 
. 032  399 
.003  813 

(■) 

7 
8 

162.0 
144.3 
128.5 

.005  071 
.008  OM 
.012  82 

.005  568 
.008  853 
.014  08 

.006  065 
.009  643 
.015  33 

9 
10 
11 

114.4 
101.9 

90.74 

.020  39 
. 032  42 
.051  55 

.022  38 
.035  59 
.056  60 

.024  38 
.038  77 
.061  64 

12 
13 
14 

80.81 
71.96 
64.08 

.081  96 
.  1303 
.2072 

. 089  99 

.1431 

.2275 

.098  01 

.1558 

.2478 

15 
16 
17 

57.07 
50.82 
45.26 

.3295 
.5239 
.8330 

.3616 
.5752 
.9146 

.3940 
.6265 
.9962 

IS 
19 
20 

40.30 
35.89 
31.96 

1.325 
2. 106 
3.349 

1.454 
2.313 
3.677 

1.584 
2. 519 
4.006 

21 
22 
23 

28.46 
25. 35 
22.57 

5.325 
8. 467 
13.46 

5.846 
9.296 
14.78 

6.368 
10.13 
16. 10 

24 
25 
26 

20.10 
17.90 
15.94 

21.41 
34. 04 
.54. 13 

23.50 
37.37 
59.43 

25.60 
40.71 
04.73 

27 
28 
29 

14.20 
12.64 
11.26 

86.07 
130.8 
217.6 

94.49 
150.2 
238.9 

102.9 
163.7 
260.2 

30 
31 
32 

10.03 

8.928 
7.950 

346.0 
550.2 

874.8 

379.9 
(i04.0 
960.4 

413.8 
657.9 
1046. 

33 
34 

3:) 

7.080 
6. 305 
5.015 

1391. 
2212. 
3517. 

1527. 
2428. 
3861. 

1663. 
2645. 
4205. 

3t; 

37 

.5.000 
4.4,53 
3.965 

5592. 

8892. 

14  140. 

6139. 

9762. 

15  .520. 

6687. 

10  {■m. 

16  9(X)'. 

39 
40 

3.531 
3. 145 

22  480. 
35  740. 

24  680. 
39  2.50. 

26  880. 
42  7.50. 

(164) 


Cable  and  Cable  Systems. — Chapter  4.  65 

STANDAKD  CABhK    CONSTANTS. 

The  standard  subterranean  rubber  insulation  cable  has  an  insulation  resist- 
ance of  about  1,800  nicf^oluns  jxir  mile,  a  capacity  of  about  0.40  microfarad  per 
mile,  and  a  copper  resistance  ot  about  37  ohms  per  mile  wlien  laid.  Average 
testing  conditions  should  show  Indelinitely  an  insulation  resistance  of  not  less 
than  500  megohms  per  mile. 

The  standard  rubber  insulation  submarine  cable  for  fire-control  and  harbor 
work  has  an  insulation  resistance  of  about  2,000  megohms  per  mile,  a  capacity 
of  about  0.48  microfarad  per  mile,  and  a  copper  resistance  of  about  17  ohms 
per  mile  when  laid.  Average  testing  conditions  should  show  indefinitely  an  in- 
sulation resistance  of  not  less  than  600  megohms  per  mile. 

The  standard  paper  insulation  cable  for  temporary  and  post  connections  hav- 
ing No.  19  B.  (k  S.  conductors  has  an  insulation  resistance  of  from  2,(XK)  to  0,000 
megohms  per  mile,  a  capacity  of  about  0.075  nncrofarad  per  mile,  and  a  copper 
resistance  of  about  43  ohms  per  mile  when  in  jjlace.  Average  testing  condi- 
tions should  show  indefinitely  an  insulation  resistance  of  not  less  than  l.OdO 
megohms  per  mile. 

The  paper  insulation  submarine  cable  has  an  insulation  resistance  as  above 
and  a  capacity  of  0.11,  with  copper  resistance  of  43  ohms  per  mile  when  laid. 
Average  testing  conditions  should  show  indefinitely  an  insulation  resistance 
of  not  less  than  1,000  megohms. 

All  of  the  above  figures  are  based  on  a  temperature  of  60°  F. 

ELECTROLYSIS. 

Where  a  subterranean  cable  system  is  so  located  that  there  is  a  po.ssibility  of 
it  being  in  the  path  of  the  return  current  of  an  electric  railway,  tests  for  the 
presence  of  electrolysis  should  be  made.  These  tests  should  be  made  during 
"  peak  of  load  "  at  railway  power  house,  if  possible. 

The  tests  consist  of  connecting  cable  sheath  of  various  cables  of  the  system  at 
various  points  to  a  positive  ground  through  a  nnllivoltraeter.  If  practicable,  the 
street  railway  track  should  be  used  for  the  ground  connection. 

If  a  reading  (regardless  of  magnitude)  is  obtained  with  the  millivoltmeter. 
the  sheath  of  cable  or  cables  should  be  permanently  grounded  at  points  where 
readings  are  obtained. 

The  usual  custom  is  to  bond  the  cables  together  and  connect  to  one  heavy 
conductor,  which  is  connected  solidly  to  the  street  railway  track  at  a  convenient 
point. 

Condemned  cable  makes  an  excellent  conductor  for  this  purpose,  the  con- 
ductors and  sheath  both  being  used  as  the  conducting  medium. 

FACTORY    TESTING    FOR    THE    ELECTRICAL    PROPERTIES    OF    CABLE. 

The  Signal  Corps  .specifications  require  the  manufacturers  to  supply  all  instru- 
ments and  facilities  necessary  for  testing  the  cable.  As  the.se  instruments  are 
different  at  the  different  factories,  a  description  of  them  will  not  be  attempted. 
At  the  beginning  of  a  series  of  tests  at  the  factory,  bridges,  condensers,  and 
high  resistances  must  be  compared  with  standards  to  verify  their  accuracy. 

The  high-voltage  test  is  first  applied  to  the  core.  The  breakdown  test  for  the 
standard  core,  after  24  hours'  inmiersion  in  water,  is  the  application  of  6.500 
volts  alternating,  for  five  minutes.  This  test  will  disclose  any  accidental  im- 
purities in  the  compound.     While  the  .specifications  require  the  application  of 

(165) 


60  Signal  Corps  Manual  No.  3.— Chapter  4. 

6.500  volts  for  five  minutes,  if  a  breakdown  occurs  it  will  occur  almost 
instantly  after  the  application  of  the  high  voltage.  One  lead  from  the  trans- 
former is  connected  witli  the  copper  of  tlie  core  and  the  other  lead  inunersed  in 
the  water  in  the  tank.  For  the  finished  cable  1,000  volts  are  applied  between 
the  armor  and  the  core  for  one  minute.  When  the  high-voltage  test  is  applied 
to  lengths  of  armored  cable  of  50  miles  or  more,  it  is,  perhaps,  better  to  use 
direct  rather  than  alternating  voltage,  to  avoid  any  possibility  of  resonance  and 
the  formation  of  stationary  waves. 

After  the  application  of  the  breakdown  test,  the  capacity,  insulation,  and 
copper  resistances  of  each  length  of  the  core  are  determined,  in  the  order  men- 
tioned. 

The  capacity  measurement  is  made  by  the  charge  method,  as  experience  has 
demonstrated  that,  using  a  low  voltage,  the  readings  at  charge  and  discharge 
are  practically  the  same,  as  the  effect  of  absorption  is  negligible.  With  some 
of  the  insulating  compounds  used  the  effect  of  the  high-voltage  test  is  to  tem- 
porarily increase  the  capacity,  and  it  will  frequently  happen  that  the  first 
measurement  may  be  higher  than  that  required  by  the  specifications,  but  if  the 
ca1)le  is  allowed  to  stand  for  24  hours  the  capacity  will  probably  drop  to  the 
limit  prescribed  by  the  specifications.  When  the  first  measured  capacity  is  too 
high  it  should  be  remeasured  after  24  hours.  When  the  capacity  of  long 
lengths  of  cable  is  being  tested,  eitlier  Thompson's  or  Gott's  method  is  prefer- 
able to  using  a  shunted  galvanometer.  In  measuring  insulation  resistance,  espe- 
cially in  damp  weather,  care  should  be  taken  to  thoroughly  insulate  the  gal- 
vanometer, keys,  and  shunt  box.  The  leakage  from  the  galvanometer  can  be 
avoided  by  connecting  the  leveling  screws  together  and  then  joining  them  to 
the  insulated  terminal  of  the  battery  key  and  by  supporting  the  leveling  screws 
on  ebonite  buttons. 

In  making  the  insulation  measurement  care  should  be  taken  to  properly 
prepare  the  ends  of  the  core,  so  as  to  avoid  surface  leakage.  The  ends  should 
be  freshly  cut  in  conical  form,  allowing  2  or  3  inches  of  the  copper  core  to 
project  so  that  the  lead  may  be  attached,  care  being  taken  that  the  freshly 
cut  surface  is  not  touched  by  the  fingers.  It  is  a  good  plan  to  dry  both  ends 
with  an  alcohol  lamp,  taking  care  that  the  flame  does  not  come  close  enough 
to  injure  the  compound. 

The  copper  resistance  is  measured  by  the  usual  bridge  method. 

In  all  cases,  at  the  beginning  of  each  series  of  tests,  the  leakage  of  the 
leads,  their  capacity,  and  resi^ance  are  determined. 

The  results  of  each  day's  work  should  be  entered  on  the  test  sheet,  and 
when  the  cable  is  finally  completed  the  data  in  respect  to  each  core  and  fin- 
ished cable  length  should  be  entered  on  the  record  sheet,  a  copy  of  which 
should  be  forwarded  with  each  shipment,  one  retained  in  the  office  of  the 
officer  making  the  inspection,  and  the  third  copy  furnished  the  Chief  Signal 
Officer  of  the  Army. 

Willie  the  logarithmic  method  of  computation  is  used  in  the  illustrations 
which  follow,  it  is  much  better  to  calculate  the  results  with  the  Thatcher 
slide  rule,  which  reads  to  four  places  of  figures  accurately,  and  by  approxima- 
tion to  the  fifth.  One  setting  of  this  rule  will  serve  for  an  entire  series  of 
calculations  and  effects  a  very  great  saving  of  time. 

In  measuring  capacity  the  method  employe<l  is  the  ordinary  ballistic  one, 
using  a  batlery  of  but  two  or  three  volts.  A  deflection  is  obtained  by  charg- 
ing a  staixlard  conden.ser,  usually  one-third  of  a  microfarad,  in  series  with  a 
galvanimictcr,  Itattery,  and  key.     The  first   throw  of  fhi>  galvniiotiieter  is  noted 

(106) 


Cable  and  Cable  Systems. — Chapter  4.  67 

-A\u\  the  (leHectiuu  for  om-  iiiicrufarad  calculatctl  ami  ciitcri'd  on  tlic  test  sheet. 
Tlie  cable  is  then  substituted  for  the  standard  eondenser,  earthiiij^  one  end 
and  the  battery,  and  the  .lellection  read  and  noted. 

In  nieasurinj^  insulation  resistance  the  galvanometer  constant  is  first  ob- 
tained by  connecting  the  higli  resistance,  usually  a  megohm,  in  series  with  the 
battery  of  100  volts,  and  galvanometer,  which  should  be  shunted  with  the  xvins 
sliunt,  and  observing  the  deflection,  which  is  then  corrected  for  the  shunt 
and  noted  on  the  test  sheet.  The  leakage  of  the  leads,  with  the  same  voltage, 
is  then  obtained.  Tlie  lead  is  then  connected  to  the  cable,  the  battery  applied, 
the  zinc  pole  to  the  cable,  and  the  other  side  grounded.  The  deflection  of  the 
galvanometer  is  noted  at  the  expiration  of  a  minute,  and  this  deflectujn  is 
tiie  one  from  whicli  the  insulation  resistance  is  calculated.  It  is  well,  how- 
ever, to  allow  the  battery  to  remain  on  for  several  nunutes,  noting  the  de- 
flection at  tlie  end  of  each  minte.  Tliis  deflection  should  fall  in  a  gradual 
and  even  manner.  In  the  case  of  one  of  the  compounds  used,  viz,  that  of  the 
Safety  companj%  the  deflection  should  halve  itself,  1.  e.,  the  insulatifin  should 
double  itself  at  the  third  and  fifth  minutes. 

After  the  insulation  resistance  has  been  obtained,  the  bridge  is  used  to 
measure  the  copper  resistance  of  the  c(tre  and  the  leads.  The  temperature  of 
the  tank  is  taken  and  noted.  All  measurements  are  made  with  the  core  or 
cable  in  the  tank  after  it  lias  been  immersed  for  24  hours,  as  the  rubber  com- 
pound will  not  attain  its  proper  insulation  at  any  given  temperature  until 
several  hours  after  it  has  reached  that  temperature.  There  is  always  more  or 
less  uncertainty  about  the  temperature,  as  the  water  in  tlie  different  parts  of 
the  tank  may  not  be  at  the  same  temperature ;  consequently  care  should  be 
taken  to  get  a  uniform  temperature  tliroughout  tlie  tank.  As  there  is  less 
uncertainty  with  the  core  than  with  the  finished  cable,  tlie  copper  resistances  of 
the  core  reduced  to  the  standard  temperature  may  be.  in  case  of  doubt,  taken 
as  a  base  for  calculating  the  test  temperature  of  the  finished  cable. 

The  insulation  resistance  of  rubber  compound  varies  with  the  temperature, 
increasing  as  the  temperature  diminishes  and  decreasing  as  it  rises.  The 
temperature  law  of  variation  of  the  insulation  resistance  can  be  taken  ap- 
proximately as  a  simple  logarithmic  law.  The  insulation  resistance,  diminish- 
ing in  equal  ratio  with  an  increase  in  the  temperature,  can  be  written  in  the 
form  />'=/•('',  in  which  R  is  tlie  resistance  at  the  higher  temperature,  r  the 
resistance  at  the  lower  temperature,  t  the  difference  in  tenqK'rature  in  <legrees 
Fahreidieit,  and  C  a  constant,  depending  on  the  nature  of  the  insulation  com- 
pound, which,  for  the  Safety  comi)any,  can  lie  assumed  as  O.OTH,  anil  for  the 
Kerite  O.OoU.  For  reilucing  the  insulation  resistance  at  any  observed  tempera- 
ture to  that  of  the  standard  temperature,  60°  F.,  it  is  necessary  to  have  a 
factor  to  multiply  the  resistance  of  the  observed  temperature.  The  O'ainife, 
Habirshaw,  and  Bishop  companies  have  found  that  their  compounds  follow  the 
logarithmic  law  sufficiently  close  for  all  iiracfical  jturposes.  The  coeflidents  of 
a  number  of  compounds,  according  to  this  simple  logarithmic  law,  are  plotted  in 
following  table  on  logarithmic  paper  <lesigned  by  the  late  Mr.  Townsend  Wol- 
cott.  The  ordinates  represent  the  temperature  and  are  plotted  arithmetically, 
while  the  abscissjie,  the  ratio  of  tlie  insulation  resistance  at  60°  F.  to  that  at  the 
temperature  of  observation,  are  plotted  logarithmically.  The  resistance  at  60° 
F.,  being  taken  as  unity,  its  logarithm,  zero",  is  in  the  center  of  the  paper,  and  the 
scale  extends  on  the  right  to  log.  VlO,  and  on  the  left  to  log.  VO.l. 


(167) 


68 


Signal  Corps  Manual  No.  3. — Chapter  4. 


The  following  table  gives  the  factors  for  reducing  the  insulation  resistance 
of  the  Okonite,  Habirshaw.  and  Bishop  companies'  compounds  to  60°  F.  accord- 
ing to  the  simple  logarithmic  law,  these  compounds  doubling  their  insulation 
with  a  difference  of  temperature  of  27°  F. 

Factors  for  retlucing  the  in^wlation  resistance  of  the  Okonite,  HabirshaiD,  and 
Bishop  compounds  to  60°  F. 


Temper- 
ature. 

K. 

LogK. 

Temper- 
ature. 

K. 

Log.  K. 

°F. 

°F. 

50 

0.773 

9. 888401 

66 

1.167 

0. 067071 

51 

.793 

9. 899629 

67 

1.197 

. 078094 

52 

.814 

9. 910802 

68 

1.228 

. 089198 

53 

.835 

9. 921906 

69 

1.260 

.  100371 

54 

.856 

9.932929 

70 

1.293 

.111599 

55 

.879 

9. 944240 

71 

1.326 

. 122544 

56 

.902 

9. 955460 

72 

1.361 

.  I33s:is 

57 

.  92.-. 

9. 966576 

73 

1. 396 

.  U4SS.> 

58 

.949 

9. 977572 

74 

1.  433 

. 156246 

59 

.974 

9.988853 

75 

1.470 

.  167317 

60 

1.000 

.000000 

76 

1.  508 

.  178401 

61 

1.026 

.011147 

77 

1.  .547 

. 1S9490 

62 

1. 053 

.  022428 

78 

1.587 

.200577 

63 

1.080 

. 033424 

79 

1.629 

. 211921 

64 

1.108 

.  044540 

80 

1.671 

.  222976 

65 

1.137 

.  055760 

As  the  result  of  careful  observations  of  the  temperature  variation  of  the 
Safety  and  Kerite  compounds,  Mr.  Townsend  Wolcott,  formerly  electrical  engi- 
neer, Signal  Corps,  gives  the  following  formula : 


Log.f§^=(.00802488+.0000446190  =  (60-0 
Log.(^J'  ^  =  (. 00845964+. 0002866040  =  (60-0 


in  which  Rt  is  the  resistance  at  the  temperature  of  ol>servation  and  /?,«,  is  the 
resistance  at  60°  F.  Calling  the  reciprocal  of  tliis  ratio  K,  the  following  table 
has  been  calculated  for  the  Safety  and  Kerite  compounds : 


(168) 


Cable  and  Cable  Systems. — ^Chapter  4.  69 

Tcmijcrutuic  corfficioil  for  the  reduction'  of  insulation  rdiintfUicc  to  U0°  F. 


Safety. 

Kerite. 

Temper- 

Temper- 

ature. 

ature. 

K. 

Log.  K. 

K. 

Log.  K. 

°  F. 

op 

50 

0.789 

9. 897441 

50 

0.591 

9.772110 

51 

.  S07 

9. 907300 

51 

.619 

9. 792:525 

52 

.826 

9.917240 

52 

.650 

9. 813104 

53 

.845 

9.927277 

53 

.683 

9. 834457 

M 

.865 

9.937396 

54 

.718 

9.856390 

55 

.886 

9. 947609 

55 

.756 

9. 878890 

56 

.907 

9. 957908 

56 

.797 

9. 901968 

57 

.929 

9. 968296 

57 

.823 

9. 92.5<)15 

58 

.952 

9. 978776 

58 

.891 

9.  949k;j6 

59 

.975 

9. 989343 

59 

.943 

9.  974632 

60 

1.000 

0.000000 

60 

1.000 

0.000(X)0 

61 

1.025 

.010746 

61 

1.061 

.025941 

62 

1.0r)0 

.021582 

62 

1.128 

.  0524.56 

63 

1.080 

.  033505 

63 

1.201 

.  079.545 

64 

1.105 

.043500 

64 

1.280 

. 107204 

65 

1.134 

.  0.54625 

65 

1.367 

.  13.5755 

66 

1.163 

.065714 

66 

1.460 

.164244 

67 

1.194 

.077098 

67 

1.562 

.  193627 

68 

1.226 

.088624 

68 

1.673 

.2235.84 

69 

1.258 

.099927 

69 

1.796 

.254106 

70 

1.292 

.111482 

70 

1.928 

.285210 

71 

1.328 

. 123120 

71 

2.074 

.316827 

72 

1.364 

.134844 

72 

2.234 

.349128 

73 

1.401 

. 146666 

73 

2.409 

.381953 

74 

1.441 

. 158564 

74 

2.602 

.415338 

75 

1.481 

.  170565 

75 

2.814 

.449310 

76 

1.523 

.  182640 

76 

3.046 

.483760 

77 

1.566 

.  194820 

77 

3.303 

.518959 

78 

1.611 

.  207090 

78 

3.  .586 

.  5546.52 

79 

1.657 

. 219431 

79 

3.899 

.590900 

80 

1.705 

.  231888 

80 

4.244 

. 627740 

The  resistance  of  copper  increases  witli  the  increase  of  temperature.  In 
order  to  i*educe  copper  resistances  at  any  temperature  between  50°  and  80°  F.  to 
60°  F.,  tlie  following  table  has  been  calculated  in  whic-li  5  is  the  factor  i).v  which 
the  resistance  at  the  observed  teni[)erature  should  be  multiplied  to  reduce  it  to 
60°  F. 

Rvduction,  of  coiipcr  rcsistdncc  to  60°  F. 


Temper- 

0. 

ature. 
°  F. 

50 

1.022 

51 

1.019 

52 

1.017 

53 

1.015 

54 

1.013 

00 

1.011 

56 

1.009 

57 

1.007 

58 

1.0(M 

59 

1.IK)2 

60 

l.()(X) 

61 

.9977 

62 

.9958 

63 

.9944 

64 

.9916 

65 

.9895 

Log.i. 


0. 009451 
.008174 
. 007321 
.  0()W66 
.  00.5609 
.004751 
.003891 
.  00.3029 
.(M)i7;{4 

.IHKIStiS 
.(MKKKX) 
9.  99iK)81 
9.998165 
9. 997551 
9.996338 
.995428 


Temper- 

S. 

ature. 

°  /•". 

66 

0. 9875 

67 

.9847 

68 

.9.s;i4 

69 

.yM3 

70 

.  9793 

71 

.9773 

72 

.  9752 

73 

.9732 

74 

.9712 

75 

.  9692 

76 

.9672 

77 

.  9l\rii 

78 

.  9633 

79 

.  9613 

80 

.9594 

Log,  5. 


9.994519 
9. 99.3614 
9. 992707 
9.99IS05 
9.  99090:{ 
9.990003 
9.  989107 
9.98.8211 
9.987317 
9. 98642.5 
9. 985.5.35 
9. 984647 
9. 983760 
9. 9828.57 
9. 981993 


The  two  following  tables  illustrate  the  manner  in  which  the  records  of  factory 
tests  are  kept,  and  the  next  is  an  example  of  a  record  sheet. 

In  the  following  where  miles  are  indicated,  statute  miles  arc  meant  unless 
nautical  miles  are  specifically  mentioned.  iNIultiply  statute  miles  by  the  factor 
1.1538  to  obtain  nautical  miles. 

(1G9) 


70 


Signal  Corps  Manual  No.  3. — Chapter  4. 


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2     P 


Cable  and  Cable  Systems. — Chapter  4. 


71 


Record  sheet. 

[Manufacturer,  Safety  Insulated  Wire  and  Cable  Company;  type,  deep-sea  cable;  loaded  on  U.  S.   Army 

transport -fiurni-jdf. J 


Section 

Length 

Capacity. 

Insulation. 

Copper. 

Core. 

Cable. 

Core. 

Cable. 

No. 

(miles). 

Core, 
per 

Cable, 
per 

Abso- 

Per 

Abso- 

Per 

mile. 

mile. 

Abso- 

Per 

Abso- 

Per 

lute. 

mile. 

lute. 

mile. 

lute. 

mile. 

lute. 

mile. 

85 

5.138 

1.988 

0.387 

1.775 

0.345 

1,613 

1,073 

90.26 

17.58 

90.32 

17. 58 

86 

5.097 

1.944 

.391 

1.635 

.321 

1,421 

1,150 

89.31 

17.52 

89.60 

17. 58 

87 

5.082 

1.775 

..349 

1.525 

.300 

1,269 

1,119 

86.36 

17.  .57 

88.92 

17.50 

88 

5.  125 

2.063 

.402 

1.610 

.314 

1,350 

778 

86.99 

17.55 

88.47 

17.26 

89 

4.855 

1.750 

.360 

1.480 

.305 

1,409 

1,108 

85.12 

17.13 

85.46 

17.61 

90 

4.853 

1.750 

.360 

1.500 

.309 

1,416 

1,077 

85.05 

17.  .52 

8.3.95 

17.  .30 

91 

4.848 

1.795 

.370 

1.613 

.333 

1,416 

1,122 

&5.  .39 

18.01 

83.95 

17.20 

92 

4.841 

1.964 

.405 

1.709 

.352 

1,637 

1,312 

84.95 

17.53 

84.25 

17.37 

93 

4.877 

1.807 

.370 

1.590 

.320 

1,487 

1,232 

85.24 

17.47 

85.31 

17.49 

94 

5.133 

1.889 

.368 

1.702 

.331 

1,510 

1,099 

89.97 

17.53 

89.32 

17.40 

95 

5.138 

2.115 

.411 

1.596 

.311 

1,610 

1,043 

90.15 

17.54 

88.46 

17.30 

96 

5.097 

1.863 

•  .365 

1.630 

.320 

1,261 

1,306 

89.11 

17.48 

87.98 

17. 26 

97 

5.112 

2.012 

.393 

1.637 

.320 

1,454 

1,039 

90.34 

17.68 

91.34 

17.87 

98 

5.098 

1.978 

.388 

1.699 

.333 

1,699 

1,306 

89.50 

17.56 

88.40 

17.35 

99 

5.107 

1.884 

.369 

1.589 

.311 

1,267 

852 

89.14 

17.46 

90.32 

17.68 

100 

5.138 

2.172 

.423 

1. 6.33 

.318 

1,358 

1,205 

90.22 

17.56 

89.40 

17.40 

The  fullowiug  coniijutatiini  illusti-ates  the  lo.narlthmic  moth(xl  of  calculatiug 
the  data  contained  in  record  sheet  of  Safety  Company  cable. 


CAPACITY. 


Loj;.  1800=3.  255273 
Log.  853=2. 930949 


Absolute  capacity,  2.110       .324324 
Log.  5.107=   .  708166 


Capacity  per  mile,  0.413     1.616158 


INSULATION   RESIST.\NCE. 


970—29=941 
Log.  185000=5.267172 
Log.         941=2.973590 


Insulation   at   temperature  of  observation,   196     2. 293582 

Log.  K  =  .207090 


Total  insulaiioii  at  60°  F.,  510     2.  501672 
Log.      5.107=   .7(KS166 


Insulation  resistance  per  mile,  1621     3.  209838 


46381°— 17- 


-12 


(171) 


72  Signal  Corps  Manual  No.  3. — Chapter  4. 

I  COPPER  RESISTANCE. 


94.5—1.38=93. 12 
Log.  93.12=1.  969043 
Log.  5        =9.983760 


Total  resistance  at  60°  F.,  87.66     1.  942803 
Log.  5.107=   .  708166 


Resistanct>  per  mile  at  60°    F..   17.16       .234637 

UATA   FOR    SAFETY    IXSCLATKD    WIKK   A.NU   CABLE    COMPANY'S    COMPOUND. 

Specific  gravity  of  conipoi'.nd,  1.(i46. 

Weight  i»er  c\il)ic  toot  of  coiiipouiul.  lo."!  iniuiuls. 

Oajjacity  per  mile,  solid  coiiduc(or= 


Capacity  per  nautical  mile,  solid  coJi<luctor= 
Capacity  ])er  mile,  7-stranded  conduct or= 


log.  Z>-log.  (/ 

2o2U 


log.  Z)  — log.  d 
.2063 


log../) -log.  2.27  8 

Capacity  i)er  nautical  mile,  7-stranded  coiiduct()r=,         ,    ^  "' 

log.  />-log.  2.27  6 

Insulation  ivsislance  jier  mile,  solid  con(luctor  =  1982   (log.  J> — log.  d). 
Insulation    resistance    per    nautical    mile,    solid    conductor=175G     (log.    1) — - 
log.  il). 

Insulation    resistance    per    mile,    7-stranded    conductor=1982     (log.    D — log. 
2.27  5). 

Insulation    resistance    per    nautical    mile,    7-sti-andt>(l    c()nductor=1756    (log. 
D— log.  2.27  5). 

Weight  i»er  mile  of  compound,  solid  core=2956   (/)" — rf"). 
Weight  per  mile  of  comi)ound,  7-stranded  conductor =2956  (/>^— 6.9  5^). 
/>  =  outsid(>  diameter  of  insulation. 
(Z=diameter  of  solid  conductor. 
5=dianieter  of  single  strand. 

PATA    I'OU    KlCKPrE. 

Spe<-ific  gravit.v  of  ••omiioiind.   1.2.">o. 
Weight  per  cubic  foot,  77  jxtunds. 

1738 

Capacity  |)er  mile,  solid  c(mductor=, '     '  , 

log.  />-log.  d 

Capacity  i)crnautic:il  mile,  solid  conductor=     — '  '    "    — -. 

log.  y>  =  log.  a 

1738 
Capacity  per  mile,  7-stran(l<'d  coiiductor=. 


log.  D-log.  2.27  6 

1  Qfi9 

Capacity  pernautical  mile,  7-8tranded  conductor=, = — ^ — t^-t^ttt 

*^  '  log.  D-log.  2.27 « 


(172) 


Cable  and  Cable  Systems. — Chapter  4. 


73 


Insulation  resistanre  jht  mile,  solid  (•(m(lu('tor=2147  lloj,'.  I*  —  !<•;;.  <l). 
Insulation    resistancv    jicr    iiautiiiii    mile.    soli<l    contluctor^^lGOL'    (loji.    D  — 
loj,'.  '/). 

Insulation    re.sistance    jter    mile,    T-stranded    (•onductor=2147     ( lo;r.    I) — lo;r. 
2.27  5). 

Insulation    resistance    per    nautical    mile,    7-straiided    <oiidu<tor=l!)(H.'    (log. 
/)— log.  2.27  8). 

Weight  per  mile  of  (•(»mi)ouiid  with  solid  (•or"^22ll  ( /)' — <l^). 
Weight  per  mile  of  compound,  7-stranded  conductor=2211    ( />'— 6.9  S"). 
Z)=outside  diameter  of   insulation. 
rf=diameter  of  solid  conductor. 
5=diaiueter  of  single  strand. 

Conversion  tables. 


statute  miles  to 
nautical  miles. 

Nautical  miles  to 
statute  miles. 

Statute 
miles. 

Nautical 
miles. 

Nautical 
miles. 

Statute 
miles. 

1 
2 
3 
4 
5 
6 
7 
8 
9 

0.  8674 
1. 7348 

2.  f)n2:{ 

3.  4697 
4.3371 
5.  2045 
6. 0719 
6. 9394 
7.8068 

1 
2 
3 
4 
5 
6 

S 
9 

1.1528 
2.30.57 
3.  4585 
4.6114 
5.  7642 
6.9170 
8.0699 
9. 2127 
10.3756 

Statute  miles  to  kilo- 
meters. 

KDometers  to  stat- 
ute miles. 

Miles         Kilome- 
^"^-           ters. 

Kilome- 
ters. 

Miles. 

1 
2 
3 
4 
5 
6 
7 
8 
9 

1. 60935 
3. 21S(i9 
4. 82S04 
6.  43739 
8.04674 
9. 65t>()8 
11.26543 
12. 87478 
14.48412 

1 
2 
3 
4 
5 
6 
7 
8 
9 

0. 62137 

1.  24274 
1.86411 

2.  48548 
3. 10685 
3. 72822 
4. 34959 
4. 9709<j 
5.59233 

(178) 


74 


Signal  Corps  Manual  No.  3. — Chapter  4. 


^4      .4S     s    .ss  .e  .es  .7  .7s  .8  .as  s  as  r. 


FIG.  4-43— COEFFICIENTS  FOR   REDUCING    INSULATION    RESISTANCE  AT 
FERENT  TEMPERATURES  TO  60°  F. 


DIF- 


(174) 


Chapter  5. 

AERIAL   LINE  CONSTRUCTION. 

The  followiiiij,-,  wliidi  aiiiioared  in  "  Tole^irapli  and  Tclcpliono  Age,  :May  10. 
191"),"  sliimltl  Ite  noted,  as  il  coincides  witli  tlie  oi)inion  of  those  wlio  hav(>  liad 
wide  experience  in  line  construction  1'or  the  Signal  Corps: 

MODEUN    1,1  NE    COXSTRfCTIOX. 

Present-day  telegraph-line  construction  is  iu  marked  contrast  with  the  notions  pre- 
vailing a  few  yt'ars  ago.  High  poles  were  then  considered  to  be  the  proper  way  of 
placing  a  line  out  of  harm's  way,  but,  with  the  constant  accretion  of  wires  and  the  in- 
creasing frequency  of  wind  and  sleet  storms,  a  revision  of  former  methods  of  construction 
became  necessary.  The  only  way  to  render  a  line  proof  against  the  extraordinary  strains 
put  upon  it  under  modern  conditions  is  to  use  shorter  and  stouter  poles.  This  now  is 
the  rule,  with  beneficial  results,  although  the  mechanical  load  and  the  violence  of 
nature's  outbreaks  still  have  to  be  reckoned  with.  The  shorter  poles  are  more  durable 
and  better  able  to  carry  their  burden  and  withstand  the  attacks  of  the  elements. 

Where  aerial  construction  is  employed,  the  system  should  be  designed  to 
utilize  cable,  as  far  as  practicable,  thereby  avoiding  a  large  number  of  aerial 
wires.  Lightning  arresters  should  always  be  installed  to  protect  cables  and 
telephones  connected  to  an  aerial  circuit.  Outside  distril>uting  wire  is  provided 
for  leading  from  the  pole  to  .substations  of  post  telephone  systems. 

ERECTION    or    LINE. 

The  route  of  the  line  having  been  decided  upon  and  the  materials  preparetl 
or  procured,  a  competent  person  should  proceed  to  measure  the  distance  and 
indicate,  by  stakes,  the  places  at  which  poles  are  to  be  erected.  When  the  line 
follows  highways  or  other  defined  routes,  he  will  necessarily  be  governed  by  the 
bounds  of  such  route  and  must  place  his  stakes  within  those  bounds  and  in  .such 
a  manner  as  to  avoid,  as  far  as  possible,  danger  to  the  line  from  pa.ssing  vehicles. 

As  a  general  rule  in  open  (unfenced)  country  the  stakes  may  be  placed  in 
.straight  lines,  but  where  there  is  a  well  defined  and  traveled  road  the  line  of 
stakes  umst  follow  the  general  direction  of  such  inad  and  be  set  at  such  distance 
from  it  that  the  line  when  completed  shall  not  l)e  exposed  to  injury  from 
passing  vehicles,  or,  in  case  a  wire  should  become  detached  from  the  insulators, 
it  can  not  by  any  chance  hang  in  the  road  and  interfere  with  or  endanger  traffic. 
With  this  in  view,  the  line  must  be  .so  placed  as  to  be  readily  inspected  ami 
examined  by  reiiair  men  from  the  road.  Whenever  practicable,  the  line  should 
be  removed  from  the  road  a  distance  of  about  30  feet.  Roads  .should  never  be 
crossed  unless  necessar.v  to  avoid  bad  ground  or  trees  which  are  too  nmnerous 
to  cut  away,  or  to  make  material  saving  by  shortening  the  line.  Such  crossings 
should  he  made  at  half  a  right  angle.  In  rolling  country,  poles  should  be 
planted  near  the  crests  of  hills  and  not  on  each  side,  as  in  the  latter  case  the 
wire  will  not  be  raised  sufficiently  high  above  the  ground  to  be  free  from  danger 
of  being  broken  by  passing  herds  or  vehicles.  As  far  as  practicable,  grade  the 
line  by  using  the  longer  poles  in  hollows  and  the  .sliorter  ones  on  high  ground. 

At  all  crossings  the  distance  between  poles  should  be  shorteneil  and  the  height 
of  wire  above  crowu  of  road  be  not  less  than  IS  feet. 

(I75t  1 


Signal  Corps  Manual  No.  3. — Chapter  5. 


Poles  should  be  preferai)l.v  of  red  cedar,  black  locnst.  or  chestnut.  Should 
these  not  be  lirocurable,  or  only  at  too  jri'^Jit  cost,  recour.se  may  be  had  to  other 
kinds  of  timber,  such  as  redwood,  white  cedar,  red  cypress,  yellow  cypress, 
tamarack,  fir,  larch,  spruce,  white  or  post  oak,  sassafras,  and  othei's.  from 
which  good  service  may  be  expected. 

All  poles  should  be  of  the  first  quality  of  live  sreen  timber,  free  from  rot,  and 
sound  and  substantial  in  every  respect.  Each  pole  should  contain  the  natural 
butt  of  the  ti'ee  and  have  an  approximately  iiniformly  decreasinc;  cross  section 
from  butt  to  top. 

All  poles  should  be  cut  between  November  1  and  March  1,  and  should  be  free 
from  all  bark  and  soft  wood.  All  knots  shoidd  be  trimmed  clo.sely  and  .smoothly. 
The  sizes  and  dimensions  of  poles  should  conform  to  the  table  below. 

When  octagonal  poles  are  ordered  they  should  be  of  the  same  material  as 
specified  for  standard  jtoles,  and  should  conform  in  general  to  the  dimensions  in 
the  table. 

Desired  (?//Hr«.s'/o«.s  of  irootl  iioU  s. 


Length  of 

Circumference. 

Length  of 

Circumference. 

poles. 

At  6  feet 

poles. 

At  fl  feet 

At  top. 

from  bot- 
tom. 

A(  top. 

from  bot- 
tom. 

Feet. 

Inches. 

Inches. 

Feet. 

Inches. 

Inches. 

20 

14 

24 

35 

22 

37 

20 

1() 

25 

35 

25 

40 

25 

16 

25 

40 

22 

40 

25 

19 

27 

40 

25 

43 

25 

22 

30 

45 

22 

45 

:» 

19 

30 

45 

25 

46 

■iO 

22 

34 

50 

22 

46 

30 

24 

36 

50 

2.5 

48 

PRESERVATIVE    TREATMENT    OF    WOODEN    POLES. 

Results  of  an  experience  with  treated  poles  over  n  period  of  18  years  by  the 
American  Telegraph  (S:  Telephone  Co.  show  that  the  life  of  poles  is  materially 
increa.sed  by  such  action. 

It  is  believed  to  be  impracticiible  to  state  the  magnitude  of  the  increase  in 
life  of  poles  obtained  by  the  use  of  preservatives,  as  the  increase  is  dependent 
upon  so  many  factors.  The  amount  of  preservative  and  depth  of  imi>regnation, 
the  kind  of  wood,  and  the  nature  of  soil  are  all  factors  which  enter  in  com- 
puting the  increase  of  life  by  using  i)reservatives.  Therefore,  suflice  it  to  state 
that  by  using  i)reservatives  the  life  of  poles,  all  things  being  equal,  is  increased 
to  such  an  extent  that  for  permanent  lines  under  ordinary  conditions  the  extra 
co.st  occasioned  by  use  of  preservative  is  more  than  compensated  for.  Tt  has 
been  found  tli;il  preservatives  not  only  delay  the  starting  of  decay  but  when 
started  tlic  decaying  effect  is  n'tarded. 

Of  I  lie  liiclors  enumerated  above  the  most  inii)ortant  oii(>  by  far  is  the  first 
one  sliown.  nanu'Iy,  the  amoinit  of  jtreservative  per  given  cubic  foot  of  wood 
and  dei)th  of  impregnation,  and  while  one  of  these  seems  to  be  dependent  upon 
the  other,  it  will  be  understood  that  the  result  of  a  heavy  coat  of  pre.servativ*' 
fin  outside  is  not  so  eflicient  as  the  same  amount  forced  into  the  pores  of  the 
wood. 


(17G) 


Aerial  Line  Construction. — Chapter  5.  3 

^here  are  three  methods  of  iipplyiiii;  preservative  in  use  at  this  time — tlie 
bnish.  the  open  tantc,  and  (he  i)n'ssure  process.  With  the  brusii  nictliod  the 
preservative  is  applied  witli  a  brush,  the  part  of  pole  to  be  treated  tirst  t)ein>; 
thoroujrhly  cleaned.  With  the  open-lank  method  the  pole  or  butt  of  pole  is 
immersed  in  a  tank  of  preservative,  the  preservative  being  kept  hot  until  bub- 
bling caused  by  air  or  water  in  poles  ceases.  The  hot  preservative  is  then 
allowed  to  cool,  and  the  vacuum  created  In  the  cells  of  the  pole  timber  while 
heating  assists  in  drawing  preservative  into  the  wood.  The  penetration  with 
the  latter  method  has  a  range  from  one-fourth  to  one-half  inch,  while  in  the 
former  ai)i)r<iximately  one-sixteenth  to  somewhat  under  one-fourth  inch  may  be 
obtained.  With  the  i)ressure  process  a  greater  penetration  is  olytaincd.  Init  ihit- 
to  cost  the  lii'st  two  methods  are  more  popular. 

Due  to  short  life  of  pine  poles,  both  above  and  below  ground,  it  is  believed 
that  such  poles  should  be  treated  their  entire  length  if  anything  approaching  a 
permanent  line  is  constructed  with  such  material.  The  part  of  any  set  pole 
most  susceptible  to  decay  is  a  section  from  a  few  inches  above  ground  line  to  2 
or  3  feet  below  ground  line,  and  where  it  is  impracticable  to  treat  wooden  poles 
thoroughly,  treatment  of  this  section  will  materially  add  to  the  life  of  the  poles. 

CONCRETE   POLES. 

In  the  Tropics,  and  occasionally  in  other  places,  it  is  more  advantageous  to 
manufacture  reinforced  concrete  poles  for  post  telephone  systems.  Concrete 
poles  are  not  recommended  for  telegraph  lines  on  account  of  the  difficulty  of 
transportation  and  delivery  along  the  route.  The  forms  may  be  easily  pre- 
pared by  using  2-inch  plank,  free  from  knots,  and  dressed  on  one  side.  Three 
pieces  only  are  required,  the  top  being  left  open  for  pouring  the  concrete.  The 
forms  are  held  in  place  by  side  and  toj)  cleats  secured  to  prevent  tlie  form 
spreading  when  the  concrete  is  poured. 

The  longitudinal  reinforcement  consists  of  four  .square  or  twisted  steel  bars, 
three-eighths  inch  bars  l)eing  about  the  proper  size  for  24-foot  poles,  and  one- 
half  inch  bars  for  longer  poles.  Tlie  four  bars  are  set  about  one-half  inch  from 
each  corner,  being  spaced  by  a  piece  of  wood  at  each  end  of  the  form,  with 
holes  to  take  the  ends  of  the  rods.  It  is  also  necessary  to  bind  the  foiu-  rods 
together  by  iron  wire  at  four  or  five  points  throughout  the  length.  The  rein- 
forcing rods  are  held  in  position  at  various  points  by  wooden  blocks  or  wire  to 
prevent  sagging.    The.se  are  removed  as  the  concrete  is  poured. 

A  very  wet  mixture  of  concrete  should  be  used,  proportioned  one  part  cement, 
two  parts  sharp  sand,  and  four  parts  crushed  stone  of  less  than  one-half  inch 
size.  It  is  important  to  have  sharp  sand.  CJravel  instead  of  crushed  stone  will 
give  satisfactory  results,  but  should  be  cleaned  well.  The  side  walls  may  be 
removed  the  next  day  after  pouring.  After  the  fourth  day  the  concrete  is 
sufficiently  set  to  remove  the  pole  from  the  bottom  form  by  sliding  it  endwi.se. 
using  heavy  ice  tongs.  A  small  anioimt  of  troweling  is  necessary  to  finish  up 
the  surfaces  before  the  concrete  is  entirely  set.  The  pole  should  be  allowed  to 
cure  about  30  days  before  use.  Wooden  pins  should  be  placed  in  the  form  be- 
fore pouring  the  concrete,  for  bolt  holes  and  pole  steps,  if  they  are  desireil. 

Concrete  poles  having  a  length  of  24  feet  should  be  about  8  by  8  inches  at  the 
base  and  5  by  5  inches  at  the  top.  Beveled  corners  improve  the  appearance. 
Twenty-four-foot  poles  weigh  approximately  1,100  pounds,  and  30-foot  poles 
1,400  pounds.  Twenty-four-foot  poles  should  be  set  approximately  4  feet  in 
the  ground,  and  30-foot  poles  approximately  .t  feet  in  the  ground.  A  24-foot 
pole  having  an  S-inch  square  base  and  a  .")-inch  square  top  requires  about  7 
cubic  feet  of  concrete. 

(177) 


Signal  Corps  Manual  No.  3. — Chapter  5, 


DIGGING    HOLES. 

The  depth  to  which  poles  should  be  set  depends  upon  the  character  of  the 
soil  in  which  they  are  placed,  the  height  of  the  pole,  and  the  load  it  is  to  carry. 
In  rock,  gravel,  or  stiff  clays  a  less  depth  is  sufficient  than  in  light  loam  or 
sand.    The  following  table  gives  the  depths  for  average  conditions: 


Length  of      Depth  in 
pole.           groimd. 

Depth  in 
solid  rock. 

Feet. 

IS 

20 
22 
25 
30 
35 
40 
45 
50 

Feet. 
(            13 
I             2  3* 

4 

5 

5?. 

6" 

6 

6^ 

7 

Feet. 

}      ^ 

3 
3 
3 

3h 
4 
4 
4i 

4 

1  On  straight  lines.     =  On  comers. 

A  foreman  follows  v.-ith  a  sufficient  number  of  men  equipped  with  digging 
bars,  spoon  sliovels,  the  ordinary  long-handled  shovel,  or  post-hole  diggers, 
where  the  soil  will  admit  of  their  use.  This  party  digs  the  holes  for  the  poles 
as  marked  out  by  the  stakes.  If  there  is  a  sod,  one  of  the  men,  equipped  with 
an  ordinary  spade,  may  be  sent  ahead  to  remove  it,  indicating  the  size  of  the 
hole  to  be  dug  and  facilitating  the  work  by  performing  a  part  thereof  for  which 
the  bars  and  spoons  are  not  well  adapted.  The  foreman  must  see  personally 
that  the  holes  are  put  down  to  the  proper  depth.  He  will  have  direction  of  the 
force  and  be  held  responsible  for  good  service.  For  poles  at  crossings,  curves, 
and  long  spans  the  holes  must  be  dug  to  a  depth  corresponding  to  the  strain  to 
be  brought  upon  them. 

POLE   SETTING. 

All  pole  holes  should  be  dug  large  enough  to  admit  the  pole  without  the 
necessity  of  cutting  away  the  butt  and  should  allow  space  to  move  the  pole 
alKiut  for  bringing  it  into  line.  Tlie  size  of  tlie  bole  .'should  be  such  that  the 
tamping  bar  may  be  used  full  depth.  This  matter  of  thorough  tamping  as  the 
hole  is  filled  is  imi)ortant  to  the  proper  .setting  of  the  pole.  On  straight  lines 
the  cross  arm  should  be  placed  at  right  angles  to  the  direction  of  the  pole  line, 
the  arms  on  adjacent  poles  facing  in  opposite  directions.  At  line  terminals  the 
cross  arms  on  the  last  two  or  three  poles  should  be  placed  on  the  sides  of  the 
poles  which  face  the  terminal.  On  curves  the  cross  arms  should  be  placed  on 
the  sides  of  the  i)oles  wliich  I'ace  the  middle  of  the  curve.  On  straight  lines 
the  poles  shall  be  set  vertically.  It  is  advisable  that  the  corner  poles  shcmld 
be  given  a  slight  rake  when  set.  varying  with  conditions,  from  10  to  20  inches. 
After  the  pole  has  been  i)laced  in  position,  the  hole  filled,  and  the  earth  well 
tamped,  the  soil  should  be  well  banked  up  about  the  pole  and  lirnily  packed  in 
place.  This  is  to  prevent  a  depression  forming  about  the  base  of  the  pole,  due 
to  subsequent  settling  of  the  earth.  In  filling  holes  the  coarse  material,  soil  or 
gravel,  should  be  used  at  the  top  of  the  boles.  Where  poles  are  set  in  rock,  the 
pieces  should  ]w  wedged  in  firmly  about  the  jjole.  It  will  usually  be  foun<l  that 
there  are  ir)ore  or  less  pronounced  cm'ves  in  all  wooden  poles.  When  setting 
the  poles  these  curves  should  be  so  placed  ;is  to  be  least  api)arent  when  vicwt'd 
from  the  direction  of  the  line. 

(178) 


Aerial  Line  Construction. — Chapter  5. 


5 


In  grading  poles  to  obtain  uniform  lielj^lit  of  lea<l  it  is  proper  to  cut  tlie  pole 
as  a  last  resort  only  when  shorter  poles  are  not  at  hand.  If  the  difference  in 
height  is  only  1  or  2  feet,  it  may  be  taken  care  of  by  digging  the  hole  deeper. 
When  necessary  to  cut  a  pole  the  top.  and  not  the  Initt,  should  be  cut. 

NUMBKK    OK    POLES. 

The  number  of  poles  to  be  provided  depends  upon  the  character  of  the  coun- 
try and  upon  the  number  of  wires  or  cables  to  be  supported.  No  less  than  the 
equivalent  of  3")  poles  per  mile  mu.>*t  be  used;  but  in  timbered  country,  with 
crooked  roads  and  heavy  leads,  it  may  be  necessary  to  increase  this  number  to 
45  or  even  more  in  si)ecial  cases. 

DELIVERY    OF    POLES. 

The  poles  should  be  delivered  as  soon  as  practicable  after  the  holes  have  been 
dug,  with  the  butt  of  the  pole  by  the  hole  and  the  top  in  the  direction  from 
which  the  raising  party  will  come.  No  equipment  is  necessary  for  this  labor, 
except  the  means  used  for  the  transportation  of  the  poles  and  carrying  hooks 
with  wbicli  to  move  them  as  required  after  unloading.  For  crossings  and  long 
spans  the  heaviest  and  longest  poles  should  be  selected ;  for  angles  and  sharp 
curves,  select  the  stoutest. 

PREPARATION   OF   POLES. 

When  practicable,  the  poles  must  be  cut  when  the  sap  is  down,  and  the 
bark  removed,  and  allowed  to  season  before  they  are  placed  in  the  line.  This 
increases  the  durability  of  most  kinds  of  poles  and  facilitates  their  transporta- 
tion and  erection.  The  tops  of  the  poles  should  be  roofed,  as  shown  in  figure 
")-!,  so  that  they  will  elTectively  shed  rain  and  snow. 

LIGHTNING  RODS. 

A  lightning  rod  is  sometimes  provided  for  every  fifth  to  tenth  pole  of  all 
aerial  lines.  This  rod  may  consist  of  a  piece  of  No.  6  galvanized-iron  wire 
extending  not  less  than  12  inches  above  the  roof  of  the  pole  and  attached  to 
the  sides  thereof  by  means  of  staples, ubout  1  foot  apart.  The  lightning  rod 
should  extend  continuously  down  the  entire  length  of  the  pole,  and  may  be 
soldered  to  a  ground  rod  driven  into  the  earth  near  the  base  of  the  pole  or 
may  be  continued  to  the  base  of  the  pole  and  there  end  in  a  small  coil  of  wire, 
to  give  good  surface  contact  with  the  earth.  This  wire  should  be  kept  as 
straight  as  possible  without  turns  or  coils  in  irs  length  and  should  be  installed 
before  the  pole  is  erected. 

CROSS    ARMS. 

The  standard  cross  arms  supplied  by  the  Signal  Corps  are  indicated  in  the 
following  table: 

IHnicnsions  of  staiulanl  (■n>s><  nniis. 


(179) 


6  Signal  Corps  Manual  No.  3. — Chapter  5. 

FKAMING  POLES. 

All  poles  supporting  cross  arms  should  be  framed  in  the  following  manner: 
Raise  the  pole  at  the  top  and  place  it  in  a  framing  buck  or  horse  so  that  the 
heaviest  sag  or  curve  will  be  nearest  the  ground.  If  the  pole  be  crooked  or 
badly  shaped,  it  should  be  turned  with  a  cant  hook  until  the  best  side  for 
framing  is  uppermost  and  the  pole  held  rigidly  in  place.  In  this  position  the 
pole  should  be  roofed.  After  the  rooting  has  been  done,  the  gains  should  be 
cut.  These  may  be  leveled  with  a  straightedge  or  sighting  stick.  To  bore 
holes  for  cross-arm  bolts,  a  line  should  be  set  off  from  the  center  of  the  top 
of  the  pole  to  the  center  of  the  butt  and  the  bolt-hole  center  laid  off  along  this 
line.  A  half-inch  hole  for  steps  niay  be  bored  at  right  angles  to  the  line  or 
in  line  with  the  cross  arms,  beginning  18  inches  from  the  lowest  cross  arm 
and  continuing  18  inches  apart  or  36  inches  apart  when  measured  on  the  same 
side  of  the  pole  until  a  point  8  feet  from  the  ground  is  reached. 


..i^.^.l 

It'-A ^-A^-i 

•«"'■"■" 

(g]|..^.„-v,.          y^f^- 

'/ 

\i''*i  'log icrew 


FOUR  PIN  ARM  ON  WOODtN  POLEL 


TWO  PIN  ARM  AND  BRACKET 
ON  WOODEIN  POLE 


IRON   ARM    ON   STEEL  POLE 


WOODEN    ARM  ilON  STEEL  POLE 


Fig.  5-1.— AERIAL   LINE  CONSTRUCTION,    PREPARATION   OF  POLES. 

All  (TOSS  arms  fur  carrying  four  wires  and  upward  must  be  brai-ed.  (Fig. 
."(-1.)     (Jains  lor  cidss  arms  will  not  e.xceed  in  any  case  1^  inches  in  depth. 

The  (lisliiiicc  Iroin  (he  uiiper  side  of  the  top  gain  to  the  extreme  top  of  the 
pole  will  !((•  s  iiichrs,  and  the  (listanc«>  bclwceu  gains  from  center  to  center 
li  feet.  Cross-arm  braces  slioidd  be  attached  t(»  the  face  of  the  pctle  and  to  the 
face  of  the  arm.  Two  lag  bolts  will  be  use<l  in  all  cross  arms  which  are  not 
braced.  Cross  arms  must  be  j)laced  on  opi)osite  sides  of  alternate  i)oles,  except 
wiiere  sjiiM-ial   conditions  of  line  wires  may  re(|uire  (»therwise. 

Cross  arms  should  Ik-  set  at  right  angles  to  the  pole  length.  This  applies 
as  well  to  <"orner  poles,  no  matter  what   the  degree  of  rake. 


(180) 


Aerial  Line  Construction. — Chapter  5.  7 

Cross-arm  fixtures  sliould.  if  inacticahU',  he  iittaclicd  lo  buildings  (other 
than  residences)  with  holts  passing  tlu'ough  the  wall.  If  this  is  not  prae- 
tical)l(\  large  exiiansidii  holts  shoidd  he  used.  Window  casenieiits  or  wcmdwork 
of  huildings  .should  never  he  used  for  resisting  the  strain  of  the  line. 


Method  of  connection 
for  iron  iv/re 


SECTION  THROUGH   CROSS    ARMS 

Fig.   5-2.— AERIAL    LINE   CONSTRUCTION,    DOUBLE   ARMING. 

Telephone  line  wires  should  not  he  terminated  at  residences  hy  means  of 
cross  arms. or  other  type  of  fixtures  attached  to  walls  of  residences.  The 
I'eason  for  this  is  that  great  aiuioyance  may  he  occasioned  hy  the  Iium  of  the 
line  wires.  Either  outside  distrihuting  or  outside  twisted  pair  wire  should  he 
invariahly  u.sed  for  .such  connections,  the  line  wire  heing  terminated  at  the 
cross  arm  or  hracket  at  nearest  pole  to  residence  and  the  service  completed  hy 
means  of  the  outside  distrihuting  or  outside  twisted  pair  wire,  which  may  he 
made  fast  to  residence  hy  means  of  a  hracket  or  other  type  of  fixture,  and 
which  should  enter  the  residence  through  two  porcelain  tuhes.  each  conductor 
of  the  duplex  wire  entering  through  one  of  the.se  tuhes.  If  practicable,  the 
tubes  should  l)e  slanted  downward  toward  the  «mtside  of  the  residence  in 
order  to  avoid  water  entering  the  tuhes  during  stormy  weather.  If  the  latter 
can  not  he  accomplislied,  the  wires  sliould  be  sagged  below  the  tubes  ou  outside 


(181) 


8 


Signal  Corps  Manual  No.  3. — Chapter  5. 


of  the  building,  whicli  will  produce  the  same  result.     The  latter  are  termed 
"  drip   loops." 

Poles  shall,  wherever  practicable,  l)e  armed  bi'fore  they  are  erected. 

Ih  lifiure  5-1  are  shown  the  methods  of  attaching,'  cross  arms  for  leads  not 
exceedinjr  four  wires,  (a)  Shows  the  four-pin  cross  arm,  with  braces;  (b)  the 
two-pin  cross  arm  attached  with  lag  bolts :  while  (c)  and  id)  show  the  methods 
pursued  in  the  case  of  steel  poles.  These  steel  poles  are  only  used  occasionally 
to  meet  special  conditions,  and  are  not  suitable  for  supporting  more  than  four 
wires  and  should  only  be  installed  in  hard  earth  or  cttncrete. 

Double  07'ms. — The  approved  method  of  installing  double  cross  arms  is  shown 
in  figure  5-2.  The  poles  upon  which  the  double  arms  are  to  be  placed  should 
)ip  selected  from  the  heaviest  of  those  available,  as  these  nuist  bear  an  addi- 
tional load,  and  extra  strength  should  be  provided.  In  tigure  .5-2  is  also  shown 
the  method  of  dead  ending  wires  on  doul)le  cross  arms.  Where  the  wire?;  are 
not  dead  ended,  but  pass  through,  they  will  be  tied  to  both  insulators  in  the 
lower  groove  of  the  glass  if  double-groove  glasses  are  in  place. 

Porcelain-coated  bridle  rings  may  be  used  for  su])porting  bridle  wire,  instead 
of  cleats  as  shown  in  figure  5-2,  and  copper  connectors  may  be  used  for  splicing 
bridle  wire  to  hard-drawn  copper  line  wire,  instead  of  as  shown  in  the  same 
figure. 

BRACKET    LINES. 

Where  not  more  than  two  wires  are  required  on  a  pole  line,  oak  brackets  may 
be  used  in  place  of  cross  arms.  The  brackets  should  be  attached  to  the  pole 
with  one  2(»d.  and  one  40d.  nails  and,  in  general,  should  oe  placed  as  shown 


BrQcMeta  must  &• 
\on  outside  </cufV9k 


Fig.   5-3.— AERIAL   LINE  CONSTRUCTION,   ATTACHING   BRACKETS. 

in  figure  .5-.3.  Where  brackets  are  jtlaced  on  i»oles,  wliicli  may  b(>  used  at  some 
biter  time  to  support  cross-arms,  tiie  loii  end  ol'  the  br.ickel  sliould  be  ab(»ul 
level  with  the  correct  location  ot  lo])  of  tiie  gain,  so  llial  I  be  i)racket  and  its 
wire  will  not  iiitertere  with  (lie  subse(nieiil  ust>  of  the  cross  arm. 


(182> 


Aerial  Line  Construction,— Chapter  5.  9 

TEKMINAL    OR    OFKK'K    I'OLE. 

Tho  toriiiiiiiil  or  office  pole  of  a  line  eiirryinj?  u  nunibei'  of  wires  is  the  most 
important  part  of  the  line  and  demands  careful  attention  to  secure  construction 
that  will  be  serviceable  and  easy  to  maintain.  There  will  be  necessity  for  fre- 
(lueiit  access  to  this  pole,  so  that  all  wiring  should  be  substantial  in  character 
and  arranj^ed  to  facilitate  repairs  and  extensions.  The  ofiice  or  terminal  pole 
shown  in  tij^ure  '>-~>  indicates  the  construction  to  be  followed  in  the  typical  case. 

It  is  probable  that  the  conditions  shown  in  tigure  .v.")  will  not  be  exactly  dupli- 
cated in  any  construction  work  which  may  be  taken  uji,  but  the  methods  shown 
should  be  followed  as  far  as  practicable. 

The  can  terminal  shown  may  be  installed  or  us«»  may  lie  made  of  a  <able  box 
shown  in  tigure  5-4.  The  hitter  is,  in  general,  considered  preferable  except  in 
tiie  Tropics.  In  (jrdering  these  boxes  the  numb(>r  of  pairs  to  be  acconuuodated 
should  be  st:ited,  as  well  as  the  number  of  pairs  of  lighlning  arresters  and  fuse.s. 
No  aerial  line  should  be  cross-coimected  at  a  terminal  pole  or  to  a  central  ex- 
change except  through  fuses  and  lightning  arresters.    The  terminal  or  cable-box 


SECTIOM  OF  DOORS 

Fig.   5-4.— AERIAL   LINE  CONSTRUCTION,    CABLE   BOX. 

poles  should  be  stepped,  using  for  this  purpose  galvanized  iron-pole  steps,  a.s 
shown  in  figure  5-5.  These  iron-pole  steps  should  not  come  do\\Ti  to  less  than 
S  feet  from  the  ground.  To  reach  these  steps,  use  may  be  made  of  a  ladder,  or 
brackets  with  the  tops  cut  off  may  be  fastened  to  the  pole  for  footholds,  as 
shown  in  figure  5-G.  Bridle  wires,  which  are  used  to  connect  the  line  wires 
with  can  terminal  or  cable  box,  run  through  hardwood  cleats,  are  shown  in 
ligure  5-2,  Particular  attention  should  be  given  to  all  wiring  about  the  pole 
to  see  that  it  fits  neatly  and  is  so  placed  that  it  will  not  be  injured  by  the 
workman  in  the  performance  of  his  necessary  duties. 

Where  the  wires  which  dead  end  on  a  double  arm  lead  from  one  direction 
only,  it  will  be  necessary  to  counterbalance  the  strain  by  running  a  small  guy 
from  this  cross  arm  to  the  next  pole. 

Linemen  should  not  use  climbers  on  poles  provided  with  steps  unless  such  use 

is  clearly  unavoidable. 

(183) 


10 


Signal  Corps  Manual  No.  3.— Chapter  5. 


GUYS    AND    ANCHORS. 


Wherever  a  pole  line  makes  a  curve,  turns  a  corner,  or  ends  iu  an  office  or 
other  terminal  pole,  particular  attention  must  be  given  to  the  matter  of  proper 


Fig.   5-5.— AERIAL    LINE   CONSTRUCTION,   TERMINAL    POLE. 

euv"  an.l  anclu.rs.  The  following-  instructions  cover  the  cases  usually  mot  with 
under  ordinary  conditions.  The  various  methods  shown  of  strengthening  the 
line  should  be  adapted  as  occasion  i-equires  to  meet  special  or  unusual  cases. 

(184) 


Aerial  Line  Construction. — Chapter  5. 


11 


Ground  fine 


Fig.  5--6._AERIAL   LINE   CONSTRUCTION.    POLE  STEPS. 
(185) 


12 


Signal  Corps  Manual  No.  3.— Chapter  5. 


Guy  stubs  and  anchor  logs.— The  timber  used  for  guy  stubs  and  anchor  logs  should 
conform  in  all  respects  with  that  specified  for  poles.  Anchor  logs  should  be  not  less 
than  24  inches  in  circiunference  nor  less  than  4  feet  in  length. 


^ 


i ^ 

a==1 

^ 

'>            '4 

.t=^-^ 

[^ 

F & 

-B 1 

»^ 

Head  guy  from  top  of  pole  I  to  bottom  of  pole  Z 
and  from  hop  of  pole,  4-  to  bottom  of  pole  3 


Fig.   5-7.— AERIAL    LINE  CONSTRUCTION,   GUYING    AT   CORNERS. 


Pig.  5-8.— AERIAL   LINE  CONSTRUCTION,  GUYING  AT   ROAD   CROSSING. 

'.\m) 


Aerial  Line  Construction. — Chapter  5. 


13 


Guy  stubs  shall  be  not  less  than  '2'2  inches  in  circumference. 

The  timber  to  he  used  for  i)oh>  liraces  shall  1)('  of  the  same  quality  as  that 
specitied  for  poles.  Braces  should  be  not  less  than  18  inches  in  circumference 
at  smaller  end. 

A  bracket  line  or  other  line  supportinj;  one  or  iwo  wires  will  not  always  re- 
quire jruys  or  braces  except  on  corner  poles  where  the  anjile  witli  the  straight 
line  approximates  90°,  and  at  road  crossings  or  terminal  poles.  Where  guys  are 
required,  it  will  usually  be  found  that  144  mils  diameter  iron  or  steel  wire, 
galvanized,  will  be  sufTiciently  heavy,  u.sed  with  a  small  deadman  or  6-inch  guy 
anchor.  Curves  of  less  than  45°  should  be  provided  for  by  giving  the  pole  th(j 
proper  rake. 


Fig.   5-9.— AERIAL    LINE   CONSTRUCTION,    GUYING    AT   CURVES. 


For  lines  carrying  six  or  more  wires  all  poles  which  are  out  of  line  should 
be  guyed.  For  a  lead  of  six  or  less  wires,  standard  guy  wire,  one-fourth  or 
five-sixteenths  inch  diameter,  will  usually  be  found  sufficient,  useil  with  a  6 
or  8  inch  guy  anchor  or  ordinary  deadman. 

On  lines  carrying  10  or  more  wires  guy  wire  should  be  not  less  than  three- 
eighths  inch,  with  not  less  than  one  8-inch  guy  anchor  or  usual  deadman. 

Wherever  a  line  makes  a  right  angle  corner  with  two  poles,  the  poles  should 
be  guyed  as  shown  at  .1.  figure  5-7.  Where  it  is  impossible  to  place  such  guys 
an   alternative   method  shown   at  B,  figure  5-7,   may   be   employed,   the   line 


4G581°— 17- 


-13 


(187) 


14 


Signal  Corps  Manual  No.  3. — Chapter  5. 


wires  between  poles  1  and  4  being  slack,  and  the  sti'ain  of  line  in  both  directions 
being  sustained  by  guys  placed  as  indicated  in  note. 

On  straight  roads  where  the  line  crosses  from  one  side  of  the  road  to  the 
other  corner  poles  should  be  guyed  as  shown  in  figure  5-8.  Terminal  poles  on 
'20-wire  lines  should  be  head  guyed,  and  if  practicable  side  guyed  in  both  direc- 
tions. When  open-wire  lines  of  20  wires  or  more  are  dead  ended  in  one  direc- 
tion only,  the  pole  adjacent  to  the  terminal  pole  should  be  head  guyed. 

The  methods  of  guying  on  curves  are  shown  in  figure  5-9. 

The  above  figures  showing  the  methods  of  guying  also  indicate  the  sides  of 
the  poles  on  which  the  cross  arms  should  be  placed  under  varying  conditions. 
In  locating  anchor  guys  the  distance  from  the  butt  of  the  pole  to  the  eye  of  the 
anchor  should  be  not  less  than  one-fifth  the  length  of  the  pole  and,  preferably, 
should  be  about  the  length  of  the  pole.  A  typical  "dead  man"  with  anchor  is 
shown  in  figure  .5-10. 

The  anchor  rod  shown  is  of  five-eighths  inch  galvanized  steel.  The  rod  passes 
through  the  anchor  log  and  is  held  in  place  by  a  nut  :ind  square  washer,  as 
shown.  The  size  of  the  anchor  log  wili  vary  with  the  depth  of  the  excavation. 
For  an  excavation  of  5  feet  in  depth  the  anchor  log  will  be  5  feet  long  and  8 
inches  in  diameter.  F'or  a  shallow  excavation  a  larger  and  longer  anchor  log 
should  be  used.  The  anchor  log,  after  being  placed  in  the  excavation,  should 
be  covered  with  planking,  as  shown.  If  this  is  not  available  logs  or  rock  may  be 
used  for  the  same  purpose.     Guys  should  be  attached  to  the  pole  innuediately 


»  a  a  a  .f'^a  a  a  «  J 


Fig.  5-10.— AERIAL   LINE  CONSTRUCTION, 
DEADMAN    AND    ANCHOR    ROD. 


Fig.  5-n.— AERIAL   LI  NE  CONSTRUCTION; 
METHOD   OF  GUYING    TO    ROCK. 


below  the  upi)er  cross  arm  or  the  lower  brack(>t,  as  shown  al  (t,  figure  5-11. 
Wiiere  144  mils  diameter  or  otiier  solid  wire  is  used  for  guy.s,  the  wire  should  be 
fastened  at  either  end  by  wrapping  the  end  about  the  main  wire.  Where 
sli-anded  wire  is  used,  the  guys  shcnild  be  fastened  at  each  end  by  means  of  an 
approved  form  of  guy  clamp,  either  two  or  three  bolt.  A  thimble  should  be 
used  for  attaching  the  guy  to  the  guy  bolt  or  guy  rod.  The  end  of  the  wire 
sliould  be  attached  to  the  stub  or  pole  and  wrapped  twice  about  this,  the  wrap- 
ping being  held  in  place  on  the  pole  or  stub  by  a  staple,  lag  .screw,  or  heavy 
nail. 


(188) 


Aerial  Line  Construction. — Chapter  5. 


15 


The  attachment  of  guys  to  tree  trunks  is  permissible,  although  when  this  is 
resorted  to  specific  permission  for  using  the  trees  must  invariably  l»e  ol)taine(l. 
In  attaching  guys  to  tree  trunks,  a  hole  slightly  larger  than  tlie  five-eigiiths  inch 
guy  rod  sliould  he  tlrilled  directly  through  center  of  tree,  a  short  distance  from 
ground.  This  distance  is  dependent  upon  the  size  of  tree,  as  with  a  compara- 
tively small  tree  the  swaying  of  the  tree  is  apt  to  loo.sen  line  if  guy  is  attached 
a  considerable  distance  from  ground.  Square  washer  and  nut  should  be  placed 
on  giiy  rod,  and  by  means  of  a  ball  hammer  the  rod  should  be  headed  over  in 
order  that  nut  can  not  readily  be  removed.  The  guy  is  attached  to  eye  of 
guy  rod  in  the  usual  manner. 

When  it  is  necessary  to  attach  a  guy  to  solid  rock,  tiie  method  shown  at  b 
of  figure  5-11  should  be  followed. 

It  may  be  found  necessary  in  some  cases  to  substitute  pole  braces  for  the  guys 
shown,  although  the  former  are  not  considered  as  desirable  a  reinforcement  as 


a    aAs    a    a 


3 1  nW  2  wra  pa  0*  ^  atrao^ 


Fig.   5-12.— AERIAL    LINE  CONSTRUC- 
TION,   POLE   BRACE. 


Fig.   5-13.— AERIAL   LINE  CONSTRUCTION. 
GUYING    ACROSS    ROAD. 


guys.  Where  pole  braces  are  used,  the  butt  of  the  brace  siiali  b.>  .spt  at  least 
31  feet  in  the  ground,  on  a  firm  support  of  planking,  stone,  or  similar  material. 
An  approved  method  of  installing  pole  braces  is  shown  in  figure  5-lL». 

Where  it  is  necessary  to  raise  guys  over  roadways  or  to  clear  obstacles,  guy 
stubs  should  be  employed,  as  shown  in  figure  5-13.  The  stubs  shoultl  have  a 
top  circumference  of  not  less  than  18  inches  and  should  be  set  in  the  ground  to  a 
depth  of  at  least  5  feet,  and  should  lean  away  from  the  pole  to  which  the  guy  is 
attached. 

In  general  practice  two  turns  of  the  guy  should  be  made  around  each  pole,  one 
end  of  the  block  attached  to  the  body  of  the  messenger  or  guy  and  the  other 
attached  to  the  free  end,  the  fall  of  the  blocks  passing  back  and  down  to  the 

(189) 


16 


Signal  Corps  Manual  No.  3. — Chapter  5. 


ground  over  a  convenient  stub  or  snatch  block.  All  anchor  guys,  head  guys,  and 
corners  should  be  pulled  with  two  sets  of  guying  blocks,  one  being  used  as  a  luff 
for  the  other  set. 

GUARD    WIRES. 

Where  guard  wires  are  necessary  to  protect  wires  from  other  wires  crossing 
above,  they  will  be  put  up  as  described  and  illustrated  below.  Referring  to 
figure  5-14,  poles  1  and  4  should  be  framed  so  as  to  leave  1  foot  of  the  pole  above 
the  top  arm.  Poles  2  and  3  should  be  framed  in  the  regular  way,  with  pin  in 
ends  of  arms,  as  shown  in  sketch.  The  upper  wires  represent  guard  wires, 
which  should  be  of  144  mils  diameter  galvanized  iron  where  the  crossing  is 


12  3  4 

Fig.   5-14.— AERIAL    LINE   CONSTRUCTION,    GUARD   WIRES. 

under  low-tension  wires.  Where  the  crossing  is  under  high-tension  wires,  stand- 
ard guy  wire  or  229  mils  diameter  wire  should  be  used  as  guards. 

The  guard  wires  terminate  on  the  top  of  poles  1  and  4,  where  heavy  porcelain 
kn(>l)s  or  other  circuit  breaks  should  be  used  when  the  crossing  is  under  high- 
tension  wires.  The  straight  lines  show  the  working  wires  as  they  will  appear 
after  guard  arms  and  wires  are  up. 

Wliere  crossing  under  a  heavy  lead  and  heavy  guard  wires  are  use«l,  guy  wires 
should  be  run  from  the  top  of  poles  1' and  4  to  a  i)oint  S  or  more  feet  from  the 
butt  of  the  next  pole  to  hold  the  strain  of  the  guard  wires. 


INSULATORS. 

The  standard  insulator  is  the  pony-porceliiiii  insulator,  double  groove.  Special 
cases  may  require  the  use  of  a  heavier  insulator,  but  in  general  the  above  type 
will  be  found  suitable. 

HTRINOING     WIRE. 

After  the  pole  line  has  been  completed,  with  all  guys,  anchors,  etc.,  in  place, 
the  stringing  of  the  wire  .should  next  be  taken  up.  The  working  party  for 
this  purpose  will  comprise  a  foreman;  a  suthcient  number  of  lin^'uien,  varying 
from  two  to  six ;  one  or  two  groundmen ;  and  such  means  of  transportation 

(100) 


Aerial  Line  Construction. — Chapter  5. 


17 


as  may  be  necessary.  The  linciiu'ii  arc  ('(luiiiiicd  witli  tools  for  sfdicinK  wire 
and  for  attai-liiii;^  it  t(»  tiic  insulators  and  nuist  be  men  who  are  able  to 
elinib  itoles  and  work  to  advaiitaf^e  thereon. 

No.  14  B.  W.  f^au^e  (81  nnls  diameter)  j?alvanizeU-iron  wire  is  sometimes 
furnished  for  temporary  local  battery  telephone  systems.  For  connnon  bat- 
tery telephone  work  No.  12  B.  &  S.  gauge  (81  mils  diameter)  hard-drawn 
bare  copper  wire  is  furnished.  This  wire  is  supplied  in  coils  of  1  mile  and 
should  be  handled  with  extreme  care  to  avoid  bruising  or  scratdiing  its  sur- 
face. Any  scratch  or  bruise  made  should  be  cut  from  the  wire  before  it  is 
installed.  Splices  should  invariably  be  made  with  copper  splicing  sleeves  fur- 
nished especially  for  this  pur])ose.     Line  splices  should  not  be  soldered. 

All  line  wire  shall  be  strung  from  pay-out  reels  in  such  manner  that  it  shall 
be  free  from  kinks  or  twists.  For  copper  wire,  ButTalo  grips  should  be  used 
so  that  it  will  not  be  injured.  For  galvanized-iron  wire,  either  a  Buflalo 
grip  or  other  form  of  clamp  may  be  used.  Wires  are  to  be  strung  with  a 
uniform  sag,  so  that  all  the  wires  on  a  cross  arm  shall  be  even.  (See  tabic 
below.)  For  short  iron-wire  lines,  and  for  copper  wire,  joints  need  not  be 
st)ldered.  Iron  wire  should  be  tied  in  with  soft  iron  wire  of  the  same  size 
as  the  line  wire.  Copper  wire  should  be  tied  in  with  pieces  of  soft  copper 
wire  of  the  same  size  as  the  line  wire. 

Sac/  of  aerial-line  wires. 


Temper- 

60-foot 

80-foot 

100-foot 

120-foQt 

140-foot 

160-foot 

180-foot 

200-foot 

ature. 

span. 

span. 

span. 

span. 

span. 

span. 

span. 

span. 

°  F. 

Inches. 

Inches. 

Inches. 

Inches. 

Inches. 

Inches. 

Inches. 

Inches. 

-  30 

0.6 

1.1 

1.9 

2.8 

3.9 

5.1 

6.5 

8.0 

-  10 

.8 

1.5 

2.3 

3.3 

4.5 

5.8 

7.4 

9.0 

-1-  10 

1.0 

1.7 

2.6 

3.8 

5.1 

6.6 

8.0 

10.4 

+  30 

1.1 

2.0 

,3.1 

4.5 

6.1 

7.9 

9.4 

12.0 

+  tiO 

1.6 

2.7 

4.2 

5.9 

7.8 

10. 0" 

12.0 

15.4 

+  80 

2.1 

3.7 

5. 6 

7.9 

10.2 

12.7 

14.9 

19.0 

-hlOO 

2.9 

.5.0 

7.2 

9.9 

12.6 

15.6 

1S.0 

22.4 

Having  provided  the  working  force  with  the  necessary  tools,  a  coil  of  wire 
is  placed  on  a  pay-out  reel,  the  binding  wires  removed,  and  the  outer  end  of  the 
wire  attached  at  the  .starting  point.  The  wire  on  the  reel  is  then  carried  along 
as  near  the  line  of  poles  as  possible,  so  that  the  wire  will  run  out  straight  and 
in  a  convenient  position  for  carrying  up.  When  a  sufficient  amount  of  wire 
has  been  run  out  it  is  carried  up  by  the  linemen  and  placed  in  a  loose  tie  on 
the  insulator.  The  groundmen  then  i)ull  the  wire  up  to  the  proper  tension,  after 
which  the  tying  in  is  completed. 

The  method  just  described  of  paying  out  wire  is  applicable  for  construction 
of  new  line  where  there  is  no  danger  of  interfering  with  trafhc  or  having  the 
wire  injured.  When  additional  wires  to  an  existing  aerial  line  are  run,  it  is 
u.sually  advisable  to  have  the  pay-out  reel  stationary.  In  such  cases  the  wire  or 
wires  (a  numl)er  can  be  pulled  at  one  time,  a  pay-out  reel  l)eing  supplied  for 
each  line)  are  attached  to  a  long  lead  rope  which  is  carrie«l  up  and  passtnl 
over  the  cross  arms.  The  latter  method  is  also  applicable  in  the  construction 
of  new  line  when  it  is  imprudent  to  have  wire  lie  on  the  ground. 

Where  more  than  one  wire  is  pulled  by  means  of  the  latter  method  the  wires 
should  be  made  fast  a  short  distance  apart  to  a  light,  strong  piece  of  wood 
termed  a  "  spreader  "  and  the  lead  or  jiulling  rope  made  fast  to  tlie  center  of  the 
spreader. 


(191) 


18 


Signal  Corps  Manual  No.  3. — Chapter  5. 


HANDLING  HARD-DRAWN  COPPER  WIRE. 


While  hard-drawn  copper  wire  possesses  hardness  and  strength  for  all  prac- 
ticable purposes,  it  will  not  stand  without  injury  the  rough  handling  to  which 
iron  wire  is  ordinarily  subjected.  ' 


Fig.   5-15.— AERIAL    LINE   CONSTRUCTION,    WIRES   ON    INSULATORS. 

Every  coil  should  be  examined  before  the  outside  cover  is  removed.  In  case 
the  covering  is  torn,  the  wire  itself  should  be  carefully  inspected  to  see  that  it 
has  not  been  cut  or  bruised.  In  case  the  wire  is  found  to  have  been  injured, 
the  injured  portion  should  be  cut  out  befoi'e  using. 


Fig.   5-16.— AERIAL    LINE   CONSTRUCTION,    WIRES   ON    INSULATORS,    CORNER    POLE. 

Copper  wire  sliould  never  be  thrown  from  an  appreciable  height. 

While  unreeling,  great  care  must  be  taken  to  avoid  twists  and  kinks.  Where- 
ever  either  is  found,  it  mu.st  be  cut  out  and  a  good  splice  made.  This  applies 
also  to  splits,  bruises,  or  indentations  of  any  kind. 


Top'i'ieyv  of  tie  without  insulator 


Commencing  tie  -  Ready  lor  cropping 


Fig.    5-17.— AERIAL    LINE    CONSTRUCTION,  TYING   H.  D.  COPPER  WIRE   TO    INSU- 
LATORS. 

(192) 


Aerial  Line  Construction. — Chapter  5. 


19 


111  tyiii;:  the  wire,  caic  niiist  Ix-  used  ii<>i  lu  lie  ii  su  t!::lit  as  to  crjiiiiii  <»r  kink 
it  l)ot\v('('n  tli«'  tic  wire  ami  tlic  ;ilass.  Hard-tliaw  ii  ccipiM-r  \vii-c  must  not  In- 
tied  with  any  wire  oIIht  tiian  soft  copix'r. 

^^■Il('ll  oiKc  liai'd-drawii  (•(•iipcr  wire  is  can'ruliy  jtnt  in  iilacc  witlioiit  kinks, 
imleiitations.  or  hniisos  it  will  stand  dianf^es  of  temperature,  sleet  storms,  etc., 
practically  us  well  as  iron  or  steel  wire  of  niucli  lower  conductivity. 


4^>^ 


^^j;^'^^ 


No  tie  must  have  feyver  than  5  tarn5 


M^^^^^^^m- 


Splicing  iron  or  steel  wire 


"mooa 


Tying  with  iron  or  steel  wire 
Fig.  5-1 


Dead  ending  iron  or  steel  wire 


AERIAL    LINE  CONSTRUCTION,  TYING  AND  SPLICING    IRON   AND  STEEL 
WIRE. 

For  straight  lines,  the  wires  should  be  placed  on  the  insulators  as  shown  in 
figure  5-15.  It  will  be  noted  that  all  wires  are  on  the  pole  side  of  the  insulators, 
except  the  middle  pair,  which  is  placed  on  the  outer  side  to  provide  a  greater 
separation.     On  corner  poles  all  wires  should  oe  placed  as  shown  in  figure  .>-lC>. 

The  approved  methods  of  tying  the  line  wires  to  the  in.sulators  are  shown  in 
figures  5-17  and  5-18.  It  will  be  noted  that  the  methods  for  iron  and  cojjper 
wires  are  different.  Soft  copper  ties  should  be  used  for  coi)per  and  soft  iron 
for  iron  or  steel  line.  Care  should  be  taken  not  to  injure  the  wire  in  tying  to 
insulator,  and  at  the  same  time  a  secure  fastening  should  be  made. 

TKA.NSl'OSniOX. 

It  may  he  found  nece.ssary  in  some  eases  to  transpose  a  metallic  circuit  to 
prevent  cross  talk  between  telephone  lines  or  interference'  from  foreign  circuits. 
Where  it  is  necessary  to  transpo.se,  the  method  shown  in  figure  5^19  should  be 
followed. 


Ftg.  5-19.— AERIAL    LINE  CONSTRUCTION,    LINE  TRANSPOSITION. 

(193) 


20 


Signal  Corps  Manual  No.  3. — Chapter  5. 


Til  making  a  transpdsition  the  use  of  coriuM-  pdles  or  curves  should  l)e  avoided 
as  far  as  practicahle. 

On  h>ng  lines  it  will  l)e  found  coiiveH'u'nt  lo  have  a  test  station  where  the  line 
may  be  opened  and  tested  both  ways  for  the  location  of  trouble.  A  form  of  test 
.station  made  on  a  two-piece  transposition  insulator  is  shown  in  tiiiure  5-20. 

RIVER    CROSSINGS. 

When  navii:cahle  streams  cross  the  routi"  of  the  line,  it  is  usually  the  lietter 
plan  to  use  submarine  cables,  except  where  they  are  liable  to  be  washed  out 
l»y  freshets;  but  if  this  method  l)e  for  any  reason  impracticable,  elevated  sup- 
ports nuist  be  used  and  the  wire  suspended  above  dani^er  from  passing  vessels. 
Natural  supports,  such  as  trees  well  rooted  in  safe  positions,  if  sucli  can  be 
found  of  sufticient  height,  may  be  used,  or  masts  erected  and  securely  stayed 
with  wire  or  wire-rope  guys.  If  the  span  between  supports  be  not  more  than 
1,500  feet,  the  line  wire  can  be  used,  care  being  fallen  to  select  the  best,  and  a 


Test  connecter- 


Fig.   5-20.— AERIAL    LINE   CONSTRUCTION,    TEST   STATION. 

length  without  .joints  or  with  joints  very  carefully  made.  For  greater  spans  a 
steel  wire  (or  compound  wire  having  a  steel  core)  is  necessary,  with  which 
spans  upward  of  2.000  feet  can  l)e  made,  provided  the  points  of  support  are  high 
enougli  to  allow  of  a  proportionately  deep  sag  to  the  wire.  Extreu'e  care  must 
be  given  to  such  crossings  <an(l  too  great  strain  avoided.  For  further  informa- 
tion and  illustrations  relative  to  river  crossings,  tlie  reader  is  referred  to  the 
subject  of  "Long  Sjians"  appearing  later  in  this  chapter. 

I, INK   COXSTKrCTION    TOOLS    AXI)    M.\TKUI.\L. 

For  complete  lists  of-  line-construction  tools  and  line-construction  niaterial, 
see  chapler  S  of  iliis  nininial.  In  submitting  reciuisition  these  lists  should  be 
followed  as  closely  as  i)ossible.  as  the  items  listed  therein  are  usually  in  stock 
at  supiily  <lei><'ts  or  may  be  pur<-hased  in  ojten  market  without  appreciable 
delay. 

Pole  lines  for  aerial  cable  should  lie  built  as  specitied  for  oi)en  wire  lines  in 
the  i»receding  jiaiM  of  this  chapter.  The  setting  and  guying  of  jxdes  should  be 
given  special  attention,  and  at  corners  and  terminal  poles  il  is  of  tirst  im- 
jiortance  tlial  the  poles  hold  their  original  positions  rigidly  if  the  cable  is  to 
remain   in  a   neat   and  workmanlike  manner  after  ert'ction.     After  the  erection 


L"  torpolc^  IO"orlc5'i indiam. 
■      lO'to  15'  ■      - 


Fig.  5-21.— ATRIAL  LINE  CONSTRUCTION,   DE^D  ENDING   MESSENGER. 

(104) 


Aerial  Line  Construction. — Chapter  5. 


21 


(if  llio  i>(»l('  line  lins  Ih'cii  ((iiniilctt'il.  with  :ill  ^'iiys,  iiiicliors.  rtc,  installod,  the 
iiicsscn^itT  win^  slioiild  lie  civctcd.  Nn(  sinjilh-r  lliiiii  I  lir»'<--»'i;rlitlis  inch  strand 
sliould  Ik'  used  for  nii'sst'n;;or.  Tlie  same  size  of  strand  that  is  usrd  for  carry- 
ini;  the  (•al)U*  shouhl  also  he  us»>d  fur  ;-'uys.  Tiic  proiicrtit's  of  various  sizes  of 
strand  are  i^iven  in  the  folluwin};  table: 


Breaking 

strain. 

Diameter 
of  strand 
in  inches. 

Lav  in 
in('he,s. 

KIont;ation  of  each  wire 
in  10  inche.s. 

Weight  per 
m)  feel. 

! 
Maximnm.     Average. 

Pounds. 
11,000 
9,000 
6,800 
4,860 
3,050 
2,000 

1 

X 

i 
rs 

4i 

^ 

4 

■iK 
3 
.  3 

Per  cent. 
13 
13 
13 

12 
12 
10 

Per  cent. 
11 

11 
11 

9 

9 

9 

Pounds. 
52 
42 
30 
22 
13 
8 

An  approved  method  of  dead  ending  messenger  wire  i.s  shown  in  figure  5-21. 

It  is  desirable  to  have  the  messenger  installed  without  splii-e,  also  to  continue 
it  past  la.st  pole  without  change  of  level,  to  a  guy  stub.  Tlie  terminal  pole  and 
stub  are  then  guyed,  as  shown  in  figure  5-22. 


Fig.  5-22.— AERIAL  LINE  CONSTRUCTION,   DEAD   ENDING   MESSENGER,  GUYING. 

Whenever  possible,  the  anchor  for  the  stub  should  be  placed  at  a  distance 
from  the  stub  equal  to  the  distance  from  the  guy  to  the  ground  level.  Tiiis  will 
give  the  anchor  guys  an  angle  of  about   ».'>  degrees.     On  all  poles  or  stults  where 


Fig.  5-23.— AERIAL  LINE  CONSTRUCTION.  SHIMS  AND  CLAMPS. 
(195) 


22 


Signal  Corps  Manual  No.  3. — Chapter  5. 


extra  heavy  steel  strand  or  niessenisrer  tU'iul  ends  or  extra  heavy  guys  are 
installed,  metal  guy  shims  should  be  used  as  shown  in  figure  r»-23. 

Thimbles  should  be  used  in  the  eyes  of  all  anelior  rods. 

Splicing  of  messenger  should  be  avoided  if  possible  l>ut  when  necessary  may 
be  done  as  follows :  Two  ends  of  the  messenger  should  be  lapped  about  6  feet. 
Three  3-bolt  clamps  should  be  put  on  in  the  center  lapping  .sections,  spacing 
them  so  that  they  touch  end  to  end.  At  each  end  of  the  outside  of  the  three 
clamps  one  Crosby  clip  should  be  placed  li  inches  from  the  three  clamps  with 
tlie  yoke  over  the  short  end  of  the  messenger  and  the  bearing  plate  on  the  main 


Detail  of  overlap  serve 


Fig.  5-24.— AERIAL  LINE  CONSTRUCTION,  SPLICING    MESSENGER. 

mes-senger.  The  end  should  be  served  up  with  overlapping  sections  of  serving 
as  shown.     The  completed  splice  is  shown  in  figure  5-24. 

Various  methods  of  attaching  the  messenger  to  poles  are  used.  Messenger 
supports  attached  with  two  lag  bolts  placed  as  shown  in  figure  5-25  are  most 
commonly  used. 

A  messenger  support  as  shown  in  figure  5-26  attached  by  a  through  bolt  may 
also  be  used.  In  ordering  supports  of  either  pattern  the  size  of  the  strand  with 
which  they  are  to  be  used  should  be  stated.  Bolts  for  attaching  are  not  fur- 
nished as  a  part  of  the  supi:)ort  and  should  be  ordered  separately.  The  mes- 
senger supports  should  be  installed  before  the  strand  is  run  out.  To  erect 
strand,  place  the  reel  on  an  axle  supported  by  two  jacks,  if  available,  and  run 
off  the  required  length  along  the  line  as  near  the  poles  as  possible.  This  is  then 
carried  up  the  pole  by  the  linemen,  the  hangers  being  already  in  place.  One  end 
is  then  dead  ended,  as  shown  in  figure  5-21.  At  the  other  end  a  pair  of  6-inch 
triple  blocks  should  be  hung  on  the  guy  stub  terminating  the  pole  line,  and  slack 
pulled  out  of  the  messenger  and  <anied  around  llie  pole  loosely  and  fastened 
with  a  clamp  for  safety.  Next,  a  l(i-iii<li  snaldi  block  is  hung  Just  below  the 
guy  shims  on  flio  side  of  the  jiole  iiarallel  willi  tiic  sIi'itI.  It  should  be  secured 
to  the  pole  with  the  equivalent  of  four  turns  of  inch  roi)e.  A  piece  of  three- 
eighths  inch  strand  measuring  KM)  feet  or  m(»re  should  be  attached  to  the  mes- 
senger by  means  of  Crosby  clips  or  three-bolt  guy  clamps  in  a  j)ermanent  man- 
ner, approximately  15  feet  from  the  stub.     Tlie  i)iece  of  strand  attached  to  the 


Fig.   5  25.— AERIAL    LINE   CONSTRUCTION, 
MESSENGER   SUPPORTS. 


Fig.  5-26.— AERIAL  LINE  CONSTRUC- 
TION. MESSENGER  SUPPORT. 
THROUGH-BOLT  TYPE. 


<19«) 


Aerial  Line  Construction. — Chapter  5. 


23 


messenger  s^hould  now  be  carried  thrnuj,'li  tlio  siiatdi  lilock  to  the  butt  of  the 
next  pole,  a  tree  or  other  sufliciently  firm  object.  A  i»air  of  lo-inch  Iriple-shoave 
hoistins  lilocks  shouhl  be  made  fast  to  this  pole  or  (»ther  object  and  lashed  with 
two  turns  of  inch  rope  or  its  equivalent.  These  blocks  should  be  attached  to 
the  strand  leading  over  the  snatch  block  with  tlie  blocks  spread  at  least  30 
feet.  A  pair  of  luff  blocks  should  be  attached  to  the  fall  of  the  main  blocks  by 
a  stopper  hitch,  allowing  the  main  fall  to  be  snubbed  around  the  nearest  s«»lid 
support.  The  slack  should  now  be  pulled  up  by  the  fall  (»f  the  luff  blocks,  using 
for  this  purpose  a  horse  or  force  of  ground  men.  The  arrangement  of  block  atnl 
tackle  described  is  shown  in  figure  5-27. 


Fig.   5-27.— AERIAL   LINE   CONSTRUCTION,    ARRANGEMENT   OF  TACKLE. 

"When  the  desired  tension  has  been  obtained,  the  main  fall  should  be  per- 
manently snubbed  and  the  messenger  made  fast.  This  is  done  by  passing  th»' 
end  twice  around  the  pole,  the  free  end  hooked  to  one  end  of  a  i)air  of  0-inch 
triple  block.s.  The  other  end  of  the.se  blocks  should  be  secured  to  the  main  mes- 
senger. The  fall  of  the.se  blocks  should  be  carried  through  a  second  and  smaller 
snatch  block  to  the  ground,  where  it  may  be  handled  with  other  luffs  to  take 
out  the  slack  in  the  messenger. 

When  this  is  done,  the  messenger  is  secured  by  Crosby  clip  and  3-bolt  guy 
clamp,  as  shown  in  figure  5-21.  The  tension  of  the  main  blocks  should  be  eased 
otT  gradually  and  with  caution  until  the  dead  end  of  the  me.ssenger  has  taken  up 
the  full  strain.  This  having  been  ctnupleted,  the  nies.senger  supports  shouhl  be 
tightened  up  on  each  pole. 

The  method  of  putting  up  messenger  just  described  is  of -general  api>iitation 
and  will  be  found  suitable  for  the  heaviest  strand  installed. 

The  messenger  should  never  turn  double  corners  or  change  from  one  sido  of 
the  street  to  the  other  by  being  pulled  around  the  corner.  (Hi  double  corners, 
messenger  and  cable  sliould  make  the  square  tiu-n,  as  shown  in  figure  5-2S.  On 
changing  sides  of  the  street  the  messenger  shoidd  terminate  at  last  iM)le,  begin- 
ning again  on  the  opposite  side  of  the  strtvt.  both  corner  polfs  being  siile  guyed 
as  well  as  lieud  guyed. 


(19T) 


24 


Signal  Corps  Manual  No.  3. — Chapter  5. 


Wlien  the  cable  is  in  place  on  the  messenger  the  sag  in  inches  should  not 
exceed  the  limits  of  the  following  table : 


Temper- 

100-foot 

120-foot 

140--foot 

160-foot 

180-foot 

200-foot 

ature. 

span. 

span. 

span. 

span. 

span. 

span. 

°F. 

Inches. 

Inches. 

Inches. 

Inches. 

Inches. 

Inches. 

-30 

12 

17| 

23i 

30J 

39 

48 

0 

12J 

17* 

24 

314 

40 

49i 

+30 

12-J 

ISJ 

25i 

:«i 

421 

521 

60 

13.} 

20 

27f 

36 

451 

5i>i 

90 

15i 

22 

30 

39i 

50i 

63  .\ 

IL'O 

18 

2o.V 

m 

421 

55 

67i 

When  pulling  the  strand  taut  allowance  should  be  made  for  the  weight  of  the 
cable,  which  will  increase  the  sag,  and  the  strand  should  lie  made  correspond- 


^ 


Fig.    5-28.— AERIAL    LINE   CONSTRUCTION,    CHANGING    DIRECTION    OF    MESSENGER. 

ingly  taut.  It  will  hardly  he  possibl(>  to  place  tlic^  strand  under  too  great  a 
tension.  As  the  strain  is  ai>plii'd.  caicrul  wnl'.-li  slioidd  Ix'  kept  for  loo.senlng 
guys  or  anchors,  buckling  of  poles,  etc.  The  blocks  should  Ite  attached  to  the 
messenger  wire  by  means  of  steel  comealongs  rather  than  buffalo  grips.  They 
may  be  attached  to  the  jxilc  or  aiii-liofngo  by  the  use  of  a  sling  of  messenger 
strand   or  manila    rope. 

c.rvs. 

If  a  single  messenger  wire  is  used  on  a  universal  hanger,  the  pole  guys  should 
be  placed  aiiovo  and  as  close  to  (he  iiiesseugei'  as  jxisible.  Tlie  guys  shoulil  be 
wrapped  twice  nlioiil   I  lie  pole  or  guy  sluli.  and  sliould  be  held  with  guy  clamps. 

Where   several    guys   ;ire   placed    >\\v    pole    lliey    sliould    be   assembled    as 

clo.sely  as  iMtssihle.  Iml  should  uo|  oxcrlap  or  hind  encli  olliei'.  When  head  guys, 
storiu  guys,  slrniid  or  other  guvs  are  fastened  1o  Hie  butt  of  llie  i>ole.  they 
should  lie  as  close  |o  1  he  ground  as  practicable,  hut  usually  not  nearer  than  H 
feet.  Cuy  stubs  slioidd  not  be  left  with  any  side  strain  whatever.  This  can  be 
jtrevenled  in  two  ways — liy  side  guying  the  stub  ilsi'lf  or  by  bringing  tiie  anclior 
rods,  stub,  and  j)oiul  of  strain  in  line. 


(198) 


Aerial  Line  Construction. — Chapter  5.  25 

Cable  raessengers  should  be  carried  at  the  lowest  level  permitted  by  existing 
conditions,  such  as  other  wires,  cables,  roadways,  etc.  The  height  of  the 
main-cable  lead  should  be  adjusted,  if  possible,  to  meet  the  requirements  of 
the  branch  or  cross  lead.  If  the  level  of  the  cable  messenger  is  to  be  changed, 
it  should  not  be  dropped  abruptly,  but  should  be  carefully  graded  to  meet  the 
requirements. 

In  serving  dead  ends  of  messenger  sufficient  length  slmulil  be  left  in  the 
messenger  or  guy  to  pass  twice  around  the  pole,  to  permit  of  the  proper  dis- 
tance between  the  end  of  the  clamp  and  pole,  and  to  allow  a  standard  length 
of  18  inches  from  the  clamp  to  the  free  end  of  the  strand.  This  free  end 
should  be  carefully  tightened  and  served  to  main  messenger  with  wrapping 
of  81  mils  diameter  iron  wire.  Where  several  messengers  or  guj'S  dead  end 
on  the  same  pole  the  ends  and  serving  should  be  lined  up. 

If  after  the  slack  has  been  pulled  out  of  a  messenger  it  ajipears  that  the 
grade  nnght  have  been  better,  it  should  be  considered  of  sufficient  importance 
to  raise  or  lower  the  support  or  supports  necessary  to  bring  this  about.  If  the 
conditions  are  favorable,  cable  supports  may  be  placed  on  the  poles  by  tape- 
line  measure  from  the  ground  to  determine  the  height.  If,  however,  the  ground 
is  uneven  or  the  conditions  are  otherwise  unfavorable  small  pieces  of  lath  or 
e(iuivalent  may  be  tacked  on  the  pole  and  raised  and  lowered  until  a  satis- 
factory grade  is  secured,  the  messenger  supports  then  being  placed  at  these 
points.  The  preliminary  pull  on  the  messenger  will  determine  the  correctness 
of  the  height  of  the  supports. 

Cable  installed  aerially  is  almost  invariably  i)aper  insulation  plain  lead 
covered. 

CABLE    HANDLING. 

Great  care  should  be  exercised  in  handling  cable,  in  transporting  it  to  the 
work  and  in  delivery  from  railroad  yartls  to  storehouses.  Cable  should  never  be 
dropped  from  a  platform  or  wagon,  and  the  reel  should  never  be  turned  on  its 
end.  Reels  will  usually  be  marked  on  the  end  with  a  heavy  arrow  showing  the 
direction  in  which  they  should  be  rolled.  The  loading  or  unloading  of  reels 
should  be  under  the  supervision  of  a  responsilile  party  ^^■ho  understands  the 
handling  of  cable. 

HANGING   CABLE. 

The  messenger  having  been  prepared  for  th'_>  cable,  galvanized-iron  rings, 
which  are  used  in  the  latest  approved  method  of  suspending  cable,  are  clamped 
tightly  to  messenger,  spacing  them  1.5  to  18  inches  apart.  The  reel  of  cable 
should  be  placed  approximately  one  .span  from  the  beginning  of  the  run  and 
supported  on  cable-reel  jacks.  A  temporary  leading-up  guy  equipped  with 
rollers  should  be  placed  in  position.  A  drag  line  for  pulling  the  cable  should 
be  brought  through  the  rings  from  the  distant  end  of  the  run  and  attached  to 
the  cable  by  suitable  means,  such  as  a  cable  gi'ip.  The  cable  may  then  be 
pulled  through  the  rings  by  means  of  a  team  of  horses,  winch,  or  a  force  of 
grouudmen.  It  may  be  necessary  to  arrange  the  galvanized-iron  rings  after 
cable  has  been  pulled,  as  one  or  more  of  the  rings  are  apt  to  slip  out  of  place 
along  messenger  during  process  of  pulling  cable. 

When  marline  hangers  are  used  they  are  made  fast  to  cable  as  it  leaves  the 
reel  by  means  of  the  marline  and  are  hooked  to  messenger  by  means  of  gal- 
vanized-iron hook  which  forms  a  part  of  the  hanger.  When  the  cable  is  pulled 
the  hooks  slide  along  the  messenger.  It  is  necessary  to  unhook  from  me.^senger 
at  each  pole  and  rehook  on  other  side.     For  this  reason  all  hangers  are  not 

(199) 


26 


Signal  Corps  Manual  No.  3. — Chapter  5. 


Fig.  5-29.— AERIAL  LINE  CONSTRUCTION.    INSTALLATION   OF   FUSED  CAN 

TERMINAL. 

(200) 


Aerial  Line  Construction. — Chapter  5. 


27 


hooked  until  (lie  pulliiij,'  of  stivt<'li  is  nearinj;  completion  or  is  foniiilclt'd. 
When  the  pulling  is  completed  all  hangers  are  spaced  equiilistant  and  hook<'<i 
to  messenger. 

PROTKCTION    or    CABLK. 

Where  cahle  is  lial)U'  lo  come  into  contact  with  wires,  tree  limhs,  guys,  or 
other  objects  which  will  injure  the  lead  sheath,  a  guard  of  wooden  strips  should 
be  put  on  and  lashed  with  marliiu>.  Tump  log  sidit  lengthwise  is  sometimes 
used  for  this  purpose. 

CABLK-BOX    UKOUNU. 

Arrester  ground  lor  <  alilc  terminal  poles  should  be  carried  straight  down  thp 
l)ole.  without  curves,  sharp  turns,  coils,  or  splices.  This  ground  should  consist 
of  a  copper  wire  of  suit:d>le  size  attached  to  a  gnmiid  plate,  coil  of  wire,  or 
ground  rod  buried  pernianeutl.v  in  moist  earth. 

I.AI'FING    FOK    SPLICING. 


Three  feet  of  lapping  section  is  all  that  is  necessary.  Whenever  necessary 
to  cut  a  cable,  as  at  the  end  of  a  run  or  otherwise,  exposed  wires  should  be 
driven  within  the  sheath  by  a  pin  or  bolt  and  the  sheath  closed  over  same  and 
sealed  with  solder.  This  is  to  be  considen><l  an  iibsolutc  rule — to  seal  all  cable 
ends  in  this  manner  innnediately  after  cutting. 

The  splicing  of  and  making  potlieads  for  all  types  of  cable  are  fully  described 
in  chapter  4. 

CONNECTIONS  TO  AEKIAI-  CABLK. 

Wlien  it  is  necessary  to  connect  aerial  wires  to  cabl(>  it  should  be  through 
fuses  and  arresters  installed  in  a  can  top  or  cable  pole  box.  A  typical  method 
of  installing  this  can  terminal  is  shown  in  figure  5-29.  where  drop  wires  are 
coimected  to  the  cable ;  the  tap  taken  out  of  the  main  cable  will  never  be  less 
than  ten  pair. 


1 

- — Hup  K        1 

-^^"^^^^B^i      K 

="^=M||i    m 

~S/>  m  6  ^j 

Fig.   5-30.— TERMINAL,    CAN,    FUSED. 


Part 

No. 


Name. 


Reference 
No. 


Base,  metal 

Mounting,  porcelain 

Spring  holaer,  complete  — 

Bolts,  clamping 

Fuse,  tubular,  .Vampere — 

Cover , 

Chain  for  cover 

Fuse  springs 

Carbons,  pr.  and  dielectric. 


1 

2 

3 

4,4 


(201) 


28 


Signal  Corps  Manual  No.  3. — Chapter  5. 


The  conductors  of  cables  are  sometimes  multiplod.  That  is  to  say,  the  same 
cable  pair  appears  in  one  or  more  terminals.  The  nuiltiple  may  be  made  in  the 
splices  or  by  bridging  pairs  at  the  binding  posts  of  terminal  boxes. 

The  paper  insulation  cable  should  be  terminated  by  a  pot  head  unless  it  ends 
in  a  terminal  equipped  with  a  sealing  chamber,  in  which  case  the  standard  pot 
head  is  not  necessary. 


3} 

i 

3! 

1 

fB 

mi 
2  ^ 

J  .-4 

1 

Fig.  5-31.— TERMINAL,  CAN,  UNFUSED. 


Part 

No. 


Name. 


Reference 

No. 


Base,  metal 

Mounting,  porcelain 

Bolts,  clamping 

Cover 

Chain  for  cover 

Binding  post,  hollow,  complete 
Binding  post,  nuts  for 


Terminals  of  lliis  character  iire  the  standard  tyi)e  furnislu'd  l)y  the  Signal 
Corps  and  are  supi)lied  in  various  sizes  up  to  and  including  52  pair  for  the  fused 
terminal  and  2(5  pair  for  the  unfused  terminal. 

Figure  5-30  shows  fused  style  of  these  terminals  and  figure  .5-31  shows  the 
unfused.  It  will  he  noted  that  the  distinguishing  difference  is  that  one  .style 
is  equipped  with  fuses  and  carboii-dielecti'ic  protc'ctors  and  the  other  is  not. 


Fig.  5-32.— TERMINAL,   CAN,   UNFUSED,    INSTALLATION   OF. 
{202  > 


Aerial  Line  Construction. — Chapter  5. 


29 


The  former  or  similar  mu's  are  invariably  used  where  aerial  open  lines  con- 
nect to  a  cable  and  the  latter  are  used  where  lines  connected  to  cables  are  not 
exposed  to  lightning  or  atmospheric  influences,  such  as  in  systems  employing 
comi>lete  underground  distribution,  or  where  connections  are  made  to  under- 
ground cable  which  is  connected  to  aerial  cable  through  fuses  and  carljon- 
dielectric  protectors.    Figure  r)-32  shows  method  of  installing  unfu.sed  terminals. 


Fig.   5-33.— TERMINAL,   CAN,    UNFUSED,    INSTALLED. 

A  brief  description  of  aerial-line  construction  employed  in  connection  with 
the  installation  of  a  post-telephone  system  at  the  Front  Royal  Remount  Depot 
near  Front  Royal,  Va.,  may  be  of  interest,  a.s  conditions  to  be  met  were  out  of 
the  ordinary.  The  post  proper,  consisting  of  the  customary  administration 
building,  oflicers'  quarters,  veterinarian  quarters,  noncommissioned  officers' 
quarters,  barracks,  dispensary,  and  otlier  structiu'es,  is  equipped  with  an 
underground-cable  system,  the  post-telephone  switchboard  being  located  in  the 
administration  building.  Communication  to  the  colt-temlers'  quarters  is  ob- 
tained by  means  of  aerial  lines  connecting  with  the  unilerground-cable  system  at 
the  boundary  of  the  post  proper.  The  colt-tenders'  quarters  are  distribute*! 
throughout  the  mountains  in  various  directions  from  the  post  proper  and  some 
are  so  located  that  to  construct  a  pole  line  to  the  quarters  would  be  au  ex- 
tremely costly  undertaking,  when  consideration  is  given  to  the  fact  that  one  sul>- 
station  only  would  be  furnished  service  by  such  construction.     Where  practi- 


46581°— 17- 


-14 


(-'Oo» 


30 


Signal  Corps  Manual  No.  3. — Chapter  5. 


Fig.  5-34.— AERIAL    LINE    CONSTRUCTION,    FENCE    POST    LINES. 


Fig.  5-35.— AERIAL   LINE   CONSTRUCTION.    FENCE    POST    LINES,   GATE   CROSSING, 


Aerial  Line  Construction. — Chapter  5, 


31 


cable  the  lines  were  supported  by  posts  of  fence  lines  inclosinjj  tlie  numerous 
pastures.  An  ordinary  oak  bracket  was  fastened  in  the  usual  manner  to  each 
side  of  alternate  fence  posts  and  No.  12  B.  W.  G.  iron  wire  was  "  tied  in  "  to 
porcelain  insulators  on  the  brackets.  In  order  to  obtain  greater  tensile  strength 
B.  B.  instead  of  standard  E.  B.  B.  grade  of  wire  was  used.  Where  gates  were  en- 
countered a  Signal  Corps  telegraph  pole  with  cross-arm  was  erected  beside  the 
gate  posts  at  each  side  of  the  gate  and  the  line  carried  over  and  above  by  tliis 
means.     Figures  5-34  and  5-35  illustrate  this  construction. 


TRIPOD    LINES. 

In  Alaska,  where  a  great  many  poles  have  been  set  in  perpetually  frozen 
ground,  great  trouble  luis  been  experienced  with  the  poles  lifting  or  "freezing 


Fig.  5-36.— AERIAL    LINE    CONSTRUCTION,   TRIPOD     LINES. 

out."  A  inunber  of  methods  lor  jireventing  such  action  have  been  tried,  but 
the  comensus  of  opinion  is  lliat  any  plan  which  contemplates  breaking  the 
surface  of  the  moss  or  earth  is  doomed  to  failure. 

Many  miles  of  lines  have  been  constructed  in  Alaska  by  the  Signal  Corps, 
wliere  poles  were  set  in  the  ground  and  in  addition  were  supported  by  braces 
in  tlie  form  of  a  tripod.  While  this  construction  proved  more  etTective  than 
former  methods,  it  was  not  satisfactory,  for,  while  tlie  braces  tended  to  hold 
the  pole  in  a  vertical  position,  the  "  freezing  out  "  was  not  eliminated  in  the 
least,  and  in  some  instances  assisted  in  lifting  the  pole,  due  to  the  ground  end 
of  the  braces  moving  in  toward  the  pole  as  it  lifted  and  preventing  pole  from 
settling  back,  if  so  inclined,  during  the  "  break  up  "  or  thawing  sea.son.  This 
operation,  repeated  for  a  few  seasons,  results  in  an  esti-emely  wobbly  and 

(205) 


32 


Signal  Corps  Manual  No.  3. — Chapter  b. 


irregular  line  and  necessitates  a  great  amount  of  traveling  and  work  in  a 
barren  country  incident  to  placing  the  line  again  in  repair. 

After  experimenting  with  various  meth(«ls,  the  Signal  Corps  has  adopted 
self-supporting  tripods  as  a  means  of  supporting  aerial  lines  where  the  con- 
ditions are  as  above  stated.  IMany  miles  of  lines  utilizing  these  tripods  have 
been  constructed,  and  resiilts  obtained  relative  to  tirst  cost  and  maintenance 
have  been  highly  satisfactory. 

Figures  5-36  and  5-37  are  reproductions  of  photograplis  of  this  approved 
tripod  construction  in  Ahiska. 


Fig.  5-37.— AERIAL    LINE    CONSTRUCTION,   TRIPOD     LINES    OVER     ICE. 

It  ciUi  |-e:nlily  be  seen  Ihat  Hn'se  Irijiods  .soiv(>  Ihe  ]ii'ol)l(>in  of  overcoming 
the  disiislidus  i-csiills  of  jmiIcs  "  Irce/.iiig  out."  but  in  addilioii  to  this  these 
(ripods  j)resent  anoliier  giTat  adxniilage  wliicii  jicrbaps  can  l)e  ai)pi'('ci;i1(>d  only 
l)y  tjiose  wlio  liave  had  ex|>eri('iice  in  connection  wilh  constructing  aciial  lines 
in  Alaska. 

(•rdinarily  I  lie  digging  of  Hie  cnsloiiiarx-  Imlcs  in  I  he  earlli  I'oi-  jiojes  is  a 
simple  umleiMakMig.  Imi  in  some  pliiccs  in  Alasl<a  Hie  elimination  of  this  i)art 
of  the  work"  by  the  sol r-sujiporl  ing  IrijMid  is.  in  itself,  a  feature  wbicli  grejitly 
reduces  llic  first  <-(isl  of  line  consti'iict  ion  and  makes  il  possible  |o  nnderlal<e 
llie  work  during  wcallier  cundilions  lli;il  <il  herwise  would  be  considei-ed  ])ro- 
Inbilive.  Cnder-  Hie  Hi  inches  or  iiioi-e  ef  lie:i\y  spagninii  mosses  found  in  nian\' 
localities  in  AUiska  the  eartli   thaws  liiil    \cry   little  excn   in  ojien  country.     To 


(20(i) 


Aerial  Line  Construction. — Chapter  5.  33 

(lis  holes,  even  late  in  the  summer,  is  almost  etiuivalent  to  digKinfr  in  set 
(•('ineiit.  DifTfiinjr  Itars  are  soon  l)lunte(l  and  must  he  scnl  to  the  tool  dresser 
daily.  Attemi»ts  to  thaw  the  ^I'ound  hy  means  of  tlie  ordinary  i)rosiK'ctor's 
holier  have  proved  unsatisfactory. 

All  material  used  in  tlie  coastruction  of  a  trijiod  line  is  comparatively  lit,'ht 
in  weifiht,  and  the  work  involved  in  construction  and  maintenance  is  less  than 
for  ordinary  pole  line.  Movinji  a  section  to  avoid  washouts,  new  roads,  or  for 
any  cau.se  is  more  easily  acconii)lishe(l. 

Tripdd    poles   can    often    he   jirocurcd    where    the    re;^ular-line   ]»oles    of    the 

dimensions  usually  required  can  not  he  found,     (i 1   I'Iihh!  material   is  ofitMi 

ohtained  from  dense  S])ruce  thickets.  The  i)oles  for  ordinary  Alaskan  line 
supporting  one  or  two  wires  should  he  18  feet  long,  with  not  less  than  3-inch 
tops,  and  fairly  straight.  They  should  be  cut  at  stump  end  with  an  axe,  not 
sawed,  as  the  long,  sharp  kerf  made  by  chopping  in  the  usual  manner  is  needed 
for  giving  the  butts  of  poles  a  hold  in  the  earth  or  moss.  If  cut  in  the  .sununer 
the  poles  should  be  peel(>d  innnediately,  as  the  bark  sets  in  a  very  few  hours, 
making  the  removal  much  more  of  a  task.  It  is  impracticable  to  peel  poles 
cut  in  the  winter,  as  there  is  comparatively  little  moisture  in  the  wood  at  that 
season. 

^Yhere  a  large  number  of  tripod  pole.s  are  to  be  cut,  it  has  been  found  advan- 
tageous to  prepare  racks  upon  which  the  poles  are  placed  and  peeled  as  soon 
as  cut.  Considerable  weight  is  lost  by  the  poles  "  drying  out,"  consequently 
I  hoy  should  not  be  transported  f<»r  several  days,  unless  the  need  for  them  be 
lU'gent. 

K1!E(  TT\(i    TiaPODS. 

After  the  right  of  way  has  been  cleared  and  iripod  poles  (.3  for  each  tripod) 
have  been  delivered  to  the  proper  location,  a  force  of  six  men  properly 
organized  proceed  to  construct  the  line.  The  three  poles  are  substantially 
lashed  together  with  144-mil  diameter  galvanlze<l-iron  wire,  approximately  2^ 
feet  from  their  small  ends,  and  the  tripods  raised  and  aligned  in  pi'oper  position. 
Oak  bi-ackets  and  insulators  are  then  placed,  as  shown  in  figures,  and  the  line 
wire  "  tied  in  "  to  the  insulator  in  the  customary  manner.  While  sucH  con- 
struction is  best  adapted  for  supporting  one  or  two  wires,  five  or  six  may  be 
supjuirted  with  less  danger  of  crosses  than  there  would  bo  with  the  ordinary 
bracket  line. 

As  with  all  line  construction.  Judgment  must  be  exercised  in  meeting  vary- 
ing conditions  when  constructing  trii)od  lines,  and  on  curves  and  corners  it 
may  be  necessary  to  guy  one  or  more  of  the  tripods  or  to  equip  their  bases 
with  three  bracing  members,  as  shown  in  figure  .VST.  This  figure  ilhistrates 
the  latter  method,  which  was  employed  in  crossing  a  shallow,  frozen  lake. 

LOXr,    SPANS. 

As  previously  stated  in  this  chapter,  where  unusually  long  aerial  spans  (over 
1,.500  feet)  are  necessary  a  special  composition  or  steel  wire  should  be  used. 
Moderately  long  .spans  can  be  made  with  galvanized-iron  wire.  In  either  case 
special  construction  is  necessary  for  resisting  the  strain,  and  .iu«lgment  nuist  be 
u.sed  in  determining  the  manner  of  insulating  the  line  and  anchoring  at  the  two 
terminals  of  such  a  span. 

The  following  illustrations  show  methods  which  have  been  adopted  for  tele- 
gi'aph  lines  of  the  Washington-Alaska  military  cable  and  telegraph  system  in 
Alaska  whei-e  it  is  necessary  to  cross  swift-current  rivers  and  mountain  gorges. 


(207) 


34 


Signal  Corps  Manual  No.  3. — Chapter  5. 


W  A'-^       1       ■^    "■     i\ 


,i>i^4ff:'  ^^m\^ 


Fig.  5-38.— AERIAL  LINE  CONSTRUCTION,  LONG  SPANS,   METHODS  OF  TERMINATING. 

(208) 


Aerial  Line  Construction. — Chapter  5. 


35 


It  will  be  noted  that  no  special   material  except   wire,  in  some  instances,   is 
required. 

Figure  5-38  shows  two  methods  of  providing  support  for  excessive  strain  of 
long  spans.  In  some  instances  l)otli  are  u.sed,  one  at  each  end  of  the  span.  The 
line  wire  is  made  fast  at  G,  laid  in  the  saddle  at  D,  pulled  up  at  saddle  at  C, 
and  made  fast  at  .strain  in.sulator  attached  to  H.  As  much  sag  as  practicable 
should  be  allowed,  as  the  strain  rapidly  increases  as  tlie  wire  is  pulled  taut. 
The  strain  of  long  span  is  not  borne  by  the  land  lines,  and  consequently  proper 
steps  should  be  taken  for  guying  the  terminal  poles  of  the,se  lines. 


Fig.  5-39.— AERIAL  LINE  CONSTRUCTION,  LONG   SPANS,  CONSTRUCTION  OF  SADDLES. 

The  poles  and  stubs  for  this  construction  should  be  as  short  as  practicable, 
but  care  should  be  taken  to  keep  the  line  wires  and  guy  fastenings  as  far  as 
practicable  above  snow  line,  as  deep  snows  will  ofttimes  .break  guy  w'ires. 


'*»••     '*«'*'<^'.K.J^ 


Fig.    5-40.— AERIAL    LINE    CONSTRUCTION,    LONG    SPANS,    ADDITIONAL    METHOD    OF 

TERMINATING. 


(209) 


36  Signal  Corps  Manual  No.  3. — Chapter  5. 

At  crossings  on  the  Yukon  River  the  l)oat  thanuel  is  on  the  bluff  side  of  the 
river  and  the  water  on  the  opposite  shore  is  usually  so  shallow  that  boats  can 
not  navijrati',  consequently  short  poles  and  stubs  can  be  conveniently  used.  At 
Ruby,  Alaska,  the  bluff  is  of  such  height  that  the  pole  supporting  the  saddle  is 
eliminated  and  the  line  wire  across  span  is  terminated  at  strain  insulators 
fastened  direct  to  stub  shown  at  H  and  G  in  figure  5-38.  While  mechanically 
the  strain  insulator  is  best  adapted  for  terminating  such  lines,  from  an  elec- 
trical viewpoint  the  glass  insulator  with  one  or  two  petticoats  properly  placed 
is  better  than  the  ordinary  sti-ain  insulator,  as  in  stormy  weather  a  film  of 
moisture  can  easily  bridge  across  the  strain  insulator  and  thereby  cause  a  heavy 
leak.  AVhere  the  latter  insulator  is  used  it  should  be  housed  by  means  of  a 
metal  funnel,  the  small  part  of  the  funnel  fitting  snugly  to  span  wire  in  order  to 
avoid  the  above-mentioned  defect. 

Figure  5-39  shows  methods  of  constructing  saddles  for  supporting  long  span 
wire.  The  method  shown  on  left  of  this  illustration  is  the  one  employed  in 
figure  5-38. 

Figure  5--i0  shows  an  additional  method  of  terminating  a  long  span  wire,  the 
wire  having  passed  over  a  saddle  which  is  not  shown  in  the  figure. 


(210) 


Chapter  6. 

POST  TELEPHONE  SYSTEMS. 

General  Orders,  No.  .5,  dated  January  28,  1913,  relates  to  post  teleplione 
systems.     Extracts  of  this  oriler  are  as  follows: 

1.  For  administrative  purposes  the  following  telephonic  comnmuications  are 
authorized  at  military  posts  and  will  be  established  by  the  Signal  Corps  as 
rapidly  as  funds  l)ei(>me  available.  Telephones  not  specitied  in  this  order  will 
be  installed  only  upon  the  approval  of  the  Chief  Signal  Officer  of  the  Army, 
and  the  specitic  need  for  each  must  be  stated  when  application  is  made  for  its 
installation : 

Office  of  the  commanding  olHcer 1 

OfHce  of  the  adjutant 1 

Office  of  the  quartermaster 2 

Office  of  the  quartermaster,  additional   (when  approved  in  each  individual 

case;  to  be  on  same  line  with  other  telephone) 1 

Office  of  the  Artillery  engineer  or  signal  officer 1 

Office  of  the  ordnance  officer 1 

Office  of  the  sergeant  major  (when  approved  in  each  individual  ca.se) 1 

Each  officer's  quarters 1 

Officers'    mess 1 

The    hospital 1 

Each  guardhouse 1 

The  post   exchange 1 

The  pumping  station 1 

Power  plant : 1 

The   corral 1 

The  quartermaster  dock 1 

Barracks  for  each  organization,  band  included 1 

Quarters  of  the  senior  master  electrician,   electrician  sergeant   at   Coast 

Artillery  posts,  or  electricians  at  interior  posts 1 

Telegraph  office  (if  located  on  reservation) 1 

Radio  station 1 

Target  range  (when  approved  in  each  individual  case) 1 

The  telephone  switchboard  will  usually  be  located  in  the  administration 
building.  Only  telephones  supiilied  by  the  Signa^  Corps  will  be  connected  in 
any  manner  to  these  sy.stems. 

In  a  number  of  instances  temporary  post-telephone  systems  have  been  in- 
stalled at  military  posts.  Almost  invariably  such  systems  are  of  local  battery 
type.  In  some  of  these  systems  underground  construction  has  been  employwl. 
in  others  aerial  construction,  and  in  others  a  combination  of  both. 

When  a  standard  system  is  authorized  for  a  post  equipped  with  a  temporary 
system,  provision  should  be  made  for  utilizing,  as  far  as  practicable,  the 
material  u.sed  in  the  temporary  system. 

For  information  relative  to  cable  system  chapter  4  of  this  marmal  should  be 
consulted.  For  information  relative  to  aerial-line  construction  chapter  5 
should  be  consulted,  and  in  chapter  8  will  be  found  complete  ,.inni'.'- "i,,..  of  all 
material  and  tools  that  will  be  required. 

The  Signal  Corps  standard  type  of  post-telephone  .system  is  coiuin.ni  r.aitery, 
utilizing  underground  construction  as  far  as  practicable.     For  telephones  at  a 

(211)  1 


2  Signal  Corps  Manual  No.  3. — Chapter  6. 

great  distance  from  post,  such  as  corral,  pumping  station,  and  small-arms 
target  range,  in  some  instances,  it  is  impracticable  to  furnish  service  under- 
gi'ound  and  aerial  construction  must  be  resorted  to. 

As  stated  In  preceding  chapter,  where  aerial  lines  are  connected  to  a  cable 
system  the  cable  must  invariably  be  protected  by  suitable  lightning  arrester. 
In  addition,  each  telephone  connected  to  an  aerial  line  must  invariably  be  pro- 
tected by  a  suitable  lightning  arrester. 

The  lightning  arrester  protecting  a  telephone  shouUl  be  located  indoors  and 
as  near  as  practicable  to  entrance  of  line. 

Figure  6-1  shows  the  Mason  lightning  arrester,  which  to  date  is  most  com- 
monly used  by  the  Signal  Corps,  and  figure  6-2  shows  an  arrester  which  is  now 
being  developed  for  installation  in  locations  that  are  damp  or  periodically  so. 


Fig.  6-1.— LIGHTNING   ARRESTER,  TELEPHONE. 


Part 
No. 


Name. 


Base,  porcelain 

Choke  coil,  left  (facing  choke  coil  end  of  arrester). . 
Choke  coil,  right  (facing  choke  coil  end  of  arrester) 

Clip,  fuse 

Clip,  carljon 

Carbon  rod  for  choke  coil 

Mica  insulators  for  choke  coil ; 

Screw,  binding,  with  nuts , 


Reference 
letters. 


Some  difficulty  has  been  experienced  with  the  type  of  arrester  shown  in 
figure  6-1  wliere  they  liave  been  installed  in  ilanip  places,  as  laundries,  due  to 
the  fact  that  vapor  cau.ses  deterioration  of  coils  and  temporary  low  insulation. 
It  is  believed  that  the  arrester  sliown  in  figure  6-2  Is  also  adapted  for  installa- 
tion in  the  Tropics,  wliere  at  certain  seasons  the  atmosphere  is  very  humid. 

Tlie  principle  in  general  upon  which  these  arresters  operate  is  that  both 
sides  of  tlie  incoming  circuit  are  made  to  pass  very  closely  to  carbon  blocks 
wliich  are  connected  electrically  and  directly  with  the  earth.  In  addition,  at 
tins  point  a  choke  coil  is  in  series  with  each  line  .so  that  a  static  charge  due  to 
liglitnlng  coming  in  on  line  wires  encounters  at  the  same  point  an  easy  path  to 
eartli  aiMl  an  impediment  in  the  path  to  instrument  the  arrester  is  protecting. 
A  bolt  of  liglitning  may  be  of  such  magnitude  and  force  that  it  will  divide, 
following  botli  paths,  ixtssibly  burning  up  arrester  and  instrument,  but  static 
cliarges  of  suflicient  magnitude  to  injure  instnnuent,  which  are  occasioned  by 
inductive  effect  of  liglitning  and  which  fic((U(Mit!y  occur,  are  efficiently  arrested 
by  these  types  of  lightning  arrester. 

(212) 


Post  Telephone  Systems. — Chapter  6. 


Fig.  6-2.— LIGHTNING   ARRESTER.   TELEPHONE,    MOISTURE-PROOF  TYPE. 


Part 
No. 


Name. 


Porcelain  block 

Cover,  brass 

Cover,  hexagon  nut  for 

Cover,  gasket  for 

Cover,  screw  for 

Binding  post,  long,  with  nuts  and  washer. . 
Binding  po.st,  short,  with  nnts  and  washer. 

Choke  coiL . : 

Carbon  blocks 

Dielectrics 

Carbon  clip 

Fu.se  clip 

Angle  clip 

Spring  clip 

Fuse  wire,  special,  feet. •- 


Reference 
No. 


Lightniiii;  arresters  for  teleplione.'^  ordinarily  liave  three  i)roteetive  features, 
viz,  fuse,  air  gap  to  ground,  and  impedance  coil.  Tlie  fuse  is  for  opening  the 
circuit  whenever  excessive  curi'ent  i'nnn  any  cau.se,  sucli  as  a  cross  of  power 
wires,  comes  in  on  the  telephone  line.  The  fuses  supplied  should  operate  for 
current  in  excess  of  one  ampere.  The  air  gap  is  u.sually  a  small  space  between 
metal  or  carbon  blocks ;  these  are  often  separated  by  celluloid  or  mica,  one  of 
these  blocks  being  in  contact  with  the  telephone  circuit  and  the  other  connectetl 
directly  to  ground.  Currents  of  excessive  volta.sie  will  break  down  the  air  gap 
going  directly  to  ground.  The  impedance  or  choke  coil  acts  as  a  Iiigh  resistance 
to  high  frequency  alternating  currents  which  come  in  on  telephone  lines,  either 
directly  or  through  induction,  and  together  with  the  air  gap  usually  lead  such 
currents  to  ground.  Fuses  operate  too  slowly  to  interrupt  lightning  or  liigh 
voltage  discharges  of  any  kind. 

It  is  important  to  note  that  where  there  is  danger  of  lines  becoming  crossetl 
with  external  circuits,  the  incoming  line  should  invariably  be  connecteil  to  fuse 
end  of  arrester,  otherwise  an  arc  to  ground  would  not  be  stopped  by  the  fuses. 
Where  there  is  absolutely  no  danger  of  lines  becoming  cros.sed  with  external 
circuits  and  where  considerable  trouble  is  occasioned  by  the  continmd  opening 
of  fuses  due  to  slight  static  dischar.ws,  the  incoming  lines  may  be  connected  to 


(213) 


4  Signal  Corps  Manual  No.  3. — Chapter  6. 

opposite  end  of  the  arrester  upon  receipt  of  special  permission  for  such  action 
from  tlie  Chief  Signal  Officer  of  the  Army. 

The  first  step  in  "  laying  out  "  a  telephone  system  for  a  post  is  to  procure  a  lar;;e, 
accurately  scaled  map  showing  all  buildings,  present  and  projective,  walks, 
roadway,  contours,  and  all  other  objects  affecting  the  location  of  telephone  lines. 
On  this  indicate  the  location  of  the  switchboard  and  all  the  telephones  to  be  con- 
nected to  it.  The  routes  of  the  various  leads  of  poles  and  course  should  now  be 
Indicated.  These  should  be  determined  only  after  personal  inspection  of  the 
ground  and  conference  with  the  post  authorities.  It  is  important  that  the 
routes  as  laid  down  in  the  first  instance  should  not  be  changed  later,  as  by  so 
doing  the  material  ordered  may  be  rendered  unsuitable,  with  resulting  expense 
and  delay  in  procuring  new  supiilies.  Avoid  changing  i)ole  line  from  one  side 
of  the  street  to  the  other.  Avoid  trees  or  other  obstacles  that  would  interfere 
with  the  line,  sharp  curves,  and  electric-power  wires.  If  aerial  construction  is 
used,  it  should  be  as  inconspicuous  as  possible;  other  things  being  equal,  run 
in  rear  of  buildings  in  preference  to  front.  It  may  be  stated  in  general  that 
ca1)le  should  be  used  where  five  or  more  i)airs  are  to  be  carried  in  one  lead. 
In  laying  out  cable  distribution,  the  future  needs  of  the  service  should  be 
provided  for  as  far  as  possible,  and  spai'e  pairs  made  availaldc. 

A  terminal  frame  is  provided  at  location  of  post-telephone  switchboard,  and 
all  lines  to  switcliboard  ternnnate  at  this  fi-anu>,  whert>  each  is  cross  connected 
to  a  suitable  protector. 

An  exception  to  this  is  made  in  installations  where  a  ternnnal  box  is  in- 
stalled in  proximity  to  switchboard,  in  which  case  the  incoming  lines  are  tei'- 
minated  at  terminal  strips  in  this  box.  In  such  instances,  by  means  of  suitable 
cabling,  th(>  inconung  lines  are  led  directly  to  protectors,  and  I'l-oni  protectors 
they  are  cross  connected  to  cable  terminals  of  IVain(>  where  Die  switchboard 
cables  are  ternunated. 

All  lines  between  protector  frame  and  switchboard  are  contained  in  switch- 
board cable,  which  is  fully  described  later  in  this  chapter. 

The  type  of  protector  frame  varies  with  size  of  installation.  Where  a  50 
or  100  line  switchboai'd  is  installed  the  protector  frame  is  usually  located  in  a 
cabinet  placed  beside  the  switchboard.  Tins  cabinet  has  the  appearance  (^f 
being  a  continuation  of  the  switchboard  cabinet.  In  larger  installations  a 
frame  termed  "distributing  fram(> "  is  installed.  This  frame  is  not  incas(>d.  but 
consists  of  angle-iron  ui)rigli1s  bolted  to  angle-iron  horizontal  members  and 
braces,  and  may  be  placed  at  a  distance  from  wall  without  being  braced  to  it. 
AVith  eitlKM*  frame,  metal  punchings  to  which  ar(>  soldered  the  inconnng  lines, 
also  a  means  of  cross  connecting  I'roni  these  punchings  to  the  jirotectors,  is 
]irovided.  ^^■illl  the  distributing  frame  lai'ge  ii'on  iMngs  coated  with  rubber  com- 
pound are  fastened  to  the  frame  at  convenient  points.  These  rings  are  for 
supporting  the  cross-connecting  wires.  Figure  G-.^  illustrates  the  construction 
and  maimer  of  cross  connecting  llie  distributing  frame. 

Various  types  of  protectors  are  i)rovided,  but  tlie  object  of  ail  is  to  ground 
the  incoming  line  in  the  event  of  a  disrui)tive  cui'rent  becoming  imi)ose(l  u])on 
the  line,  thereby  ol)viating  damage  to  switchboard.  All  protectors  are  provided 
with  carbons  and  dielectrics.  These  carbons  and  dielectrics  consist  of  two  car- 
bon lilocUs  anil  one  dieleclric  I'oi-  each  side  of  eacii  circuit.  The  incoming  line 
is  in  eleclrical  conlract  willi  one  of  the  cai'bon  blocks  and  Ihe  oilier  carbon 
block  is  ill  (jiri'cl  coiila<'t  with  a  nietiil  plate  which  is  elect  rica!l.\'  connected  to 
earth.  The  dielectric,  which  consists  of  nii(;i  or  celluloid  api»roxiniately  1  mil  in 
thickness,  the  other  dimensions  being  same  ms  width  and  length  of  carbon  block, 


Post  Telephone  Systems.— Chapter  6. 


Fia    6-3.— FRAME,    DISTRIBUTING,   TELEPHONE   SWITCHBOARD. 


(215) 


6  Signal  Corps  Manual  No.  3. — Chapter  6. 

is  placed  between  the  blocks,  thereby  insulating  one  from  the  other.  The 
dielectric  is  either  perforated  or  has  a  small  U-shaped  piece  removed  so  that 
a  dangerous  current  will  have  merely  a  small  air  gap  to  break  down  in  order 
that  it  will  be  dissipated  in  the  earth.  Static  or  oscillating  currents  of  high  E. 
M.  F.  and  high  potential  circuits  will  be  grounded  by  the  part  of  the  protector 
just  described,  but  a  current  of  comparatively  low  E.  M.  F.  that  would  in  time 
burn  out  windings  of  switchboard  would  not  be  grounded  by  this  means ;  con- 
sequently each  protector  is  also  provided  with  what  is  termed  a  "  heat  coil,"  with 
suitable  mounting,  for  arresting  the  latter  currents.  These  currents  are  com- 
monly termed  "  sneak  currents." 

In  one  type  of  these  heat  coils  the  passage  of  a  "  sneak  current "  causes 
the  line  to  be  opened  and  the  line  side  groundetl.  In  another  type  the  line  is 
merely  grounded.  In  either  case  the  operation  of  the  coil  is  caused  by  the 
current  heating  to  a  point  of  "  cold  flow "  solder  which  normally  holds  a 
spring,  which  is  in  contact  with  line,  clear  of  ground  plate.  The  heating  is 
accomplished  by  means  of  a  winding  in  some  instances  and  in  others  by  a  spe- 
cially prepared  composition.  The  winding  or  composition  is  in  series  with  the 
incoming  line  and  is  so  designed  that  heat  is  generated  when  a  dangerous  cur- 
rent passes  through  the  heat  coil.  The  time  element  of  operation  of  these 
coils  is  inverse  to  the  strength  of  current. 

Currents  induced  by  lightning  act  too  rapidly  for  fuses  or  heat  coils,  and 
although  such  currents  frequently  accomplish  unaccountable  i-esults  the  car- 
bon-dielectric part  of  switchboard  protectors  almost  invariably  ground  these 
currents. 

The  crossing  of  telephone  lines  with  lighting  circuits  might  complete  a  cir- 
cuit through  switchboard  w'hich  would  burn  out  all  coils  in  its  path  and  yet 
be  of  such  E.  M.  F.  that  the  carbon-dielectric  part  of  arrester  would  not  act. 
The  heat  coil  portion  of  arrester  would  ground  and  dissipate  such  a  current 
before  damage  to  switchboard  could  result. 

COMMON    HATTKIIY    I'OST-TKT.Kl'HOX  K    S  W  ITCI I  HOAKDS. 

Vnrioiis  types  oC  ('.  15.  tclc|)li(iiH>  switclibonnls  liavc  been  installed  at  Army 
posls. 

The  following  dislinguisliing  f(>alun>s.  which  arc  ]»f(iminciil  in  idciit  il'ying 
(he  various  types,  nvv  believed  to  l)e  wctrlhy  of  mention  : 

1.  \'isu;il  siguMls  for  line  signal  and  visual  signals  for  siii)ervisory  signal. 

2.  Visual  signals  for  line  signal  and  lamp  signals  for  supervisory  signal. 
8.  Lamp  signals  for  line  signal  and  lamp  signals  for  supervisory  signal. 

In  most  instances  the  keys  are  double  ringing,  although  some  of  the  switch- 
boards installed  in  connection  with  early  installations  were  equipped  with 
the  single  ringing  type.  With  the  double  ringing  key  the  switchboard  ojierator 
is  enabled  to  ring  on  eiljier  of  the  two  lines  which  have  be(>n  connected  by 
means  of  the  switchboard  connecting  coi-d.  ■\Villi  the  siiigl(>  ringing  key.  it  is 
po.ssible  to  ring  on  one  line  only,  unless  tlu'  connt>cting  cords  are  transposed. 

Some  of  the  conmion  battei-y  switchboards  purchased  by  the  Signal  Corps 
are  designed  to  operate  on  a  30- volt  circuit  while  others  ar(>  designed  to 
operate  on  a  24-volt  circuit.  Care  should  be  exercised  nol  1o  operate  the 
24-volt  sigriid  lamps  on  .SO-volt  circuit,  as  tlicir  life  is  greatly  decreased  by  the 
excessive  voltage. 

A  description  of  switchboard  e()uipped  with  "visual  signals  for  line  signals 
and  visual  signals  for  supervisory  signals"  follows.  The  circuit  of  the  system 
where  a  switchboard  of  this  type  is  used  is  shown  diagrammatically  in  figure 
6-4,    'The  instruments  \ised   in   connection    with    this  switchboard   conform   in 


Post  Telephone  Systems. — Chapter  6. 


wiring  nnd  design  to  well-known  coininerciiil  standiirds,  and  the  operation  of 
the  switchboard  is  fully  explained  hereinafter. 

To  signal  the  switchboard  (tig.  G-5)  it  is  merely  necessary  to  remove  the 
receiver  from  the  hook,  which  permits  direct  current  to  flow  from  the  common 
battery  through  the  line  signal,  one  contact  of  the  cut-off  jack,  the  line,  the 
hook,  the  windings  of  the  induction  coil,  the  transmitter,  line,  the  jack,  and 
back  to  battery.  This  causes  the  line  signal  to  close,  attracting  the  attention 
of  the  operator. 


%im. 


24  or  30  Vo/ts 
Storage,  Bati^ry 

Fig.  6-^.— C.   B.  TELEPHONE  SYSTEM,   SIMPLIFIED   DIAGRAM    OF  CIRCUITS. 

Referring  to  figure  6-4,  when  the  switchboard  connection  is  made,  disre- 
garding detail  of  switchboard  circuits,  current  flows  from  the  common  battery 
through  the  supervisory  signal,  the  lines  in  parallel  to  each  transmitter, 
induction  coil,  hook,  line,  and  back  through  supervisory  signal  to  battery. 
The  supervisory  serves  the  dotible  purpose  of  providing  the  necessary  retarda- 
tion, as  previously  described,  under  the  composite  circuit  and  of  indicating  t<i 
the  operator  that  the  conversation  has  been  completed. 


Line  Signa/ 


ii|i|i|a|i{i|i|iii|i|i|i|i|i|i-' 

30  Vo/ts 


Fig.  6-5.— C.    B.   TELEPHONE   SYSTEM.   VISUAL   LINE   SIGNAL  OPERATION. 

^217) 


signal  Corps  Manual  No.  3. — Chapter  6. 


The  instrument  circuit  of  one  of  tlie  types  of  common  battery  telephones 
used  is  out  of  the  ordinary  and  is  sliown  in  figure  6-5.  It  employs  the  principle 
of  the  balanced  \Yheatstone's  bridge  to  keep  the  direct  current  flow  from  the 
receiver,  while  the  voice  currents,  which  are  alternating  in  effect,  are  forced 
by  a  combination  of  retardation  and  low  resistance,  located  in  the  arms  of 
the  bridge,  through  the  receiver.  A  and  D  are  retardation  coil  windings  and 
B  and  C  noninductive  resistance  windings.  The  bridge  is  balanced  for  the  direct 
current  flow,  indicated  by  the  single-pointed  arrows,  by  making  the  ohmic  re- 
sistance of  the  four  arms  such  that  the  Wheatstones'  bridge  equation,  A:B  = 
C:D,  is  balanced.  There  will,  then,  be  no  direct  cun-ent  flow  between  the 
points  2  and  3,  as  their  potential  is  the  same,  and  the  receiver,  which  takes  the 
place  of  the  galvanometer  in  the  i-egular  testing  bridge,  will  be  entirely  free 
from  direct-current  action.  The  bridge,  however,  is  completely  out  of  balance 
for  voice  currents,  which  can  not  penetrate  the  high  retardations  .1   and  D, 


rRONT   VIEW  VERTICAL   SECTION 

Fig.  6-6.— SWITCHBOARD,   TELEPHONE,   C.   B.,   50-LINE,   VISUAL. 


Post   Telephone  Systems. — Chapter  6. 


Part 
No. 


Name. 


Reference 
So. 


Binding  post,  lock-nut 

BitulinR  post ,  wing-nut 

MeM,  night 

Boll,  night,  binding-post  nuts 

BpII,  night,  relay 

Cable,  switcli board,  feet 

Cord,  -l-way,  for  tninsmiller  and  receiver 

Cord,  switcliboard,  complete,  with  terminals 

Cord  weight ;■. . 

Cord  bushing 

( 'ord  plug  screw 

Cord  plug  sliell  screw 

Cord  plug  seat  with  screws 

Cord  fastener,  complete,  with  screw  s .• 

Coil,  induction 

Coil,  induction,  terminals 

Coil,  impedance,  for  operator's  circuit 

Condenser,  2  m  f 

(ienerator,  five-bar 

Generator  crank 

(ienerator  crank  liandle 

Jack,  line 

Jack,  generator  call 

Key,  ringing,  complete 

Key,  ringing^  ban  lie 

Key,  answermg,  complete 

Kev,  answering,  handle  for 

Line  terminal 

Re:>eiver,  single  head 

Signal  generator  call,  complete 

Signal  generator  call,  drop 

Signal  generator  call,  adjusting  screw  and  nut 

Signal  generator  call,  moimting  screw 

Signal  generator  call,  armature  mounting  screws. . 

Signal  generator  call,  armature  pivots 

Signal,  line,  complete 

Signal,  line,  drop 

Signal,  line,  a<ljiist  ing  screw  with  nut 

Signal,  lino,  mounting  screw 

Signal,  line,  armature  mounting  screws 

Signal,  line,  armature  pivots 

Signal,  supervisory,  complete 

Signal,  suiiervisory,  drop , 

Signal,  supervisory,  adjusting  screw  with  nut 

Signal,  sujiervisory,  mounting  screw 

Signal,  supervisory,  armature  mounting  screws. . . 

Signal,  supervisory,  armature  pivots 

Switcli,  transmit  ter , 

Switch,  transmitter,  han  ile , 

Switch,  transmitter,  crank  with  screw 

Switch,  transmitter,  stop  pins 

Switch,  battery  test  (same  as  transmitter  switch). 

Switch,  night  bell  (same  as  transmitter  switch) 

Transmit  ter 


and  are  thus  forceil  tliroii.^h  tlie  receiver  and  intiiindiiorive  resistances  Ji  and  (' 
in  tlie  path  indicated  by  tlie  doiible-lieaded  arrows.  In  practice  all  of  the  coils 
of  this  briilfio  are  wound  on  one  spool  and  internally  connected,  so  that  as  far 
as  external  appearances  or  connections  are  concerned  it  resembles  a  standard 
induction  coil.  The  resistance  of  the  four  windinjrs  are  approximately  20  ohms 
each  for  .1  and  B  and  30  ohms  each  for  C  and  /).  The  total  resistance  of  the 
noninductive  windinjrs  B  and  (\  which  are  in  series  with  the  receiver,  is  there- 
fore only  oO  ohms,  thus  offering:  no  appreciable  ol»stacle  t<»  the  voice  currents. 
In  fact,  the  receiver  is  practically,  in  the  line  circuit,  direct,  and  receives  the 
maximum  available  incoming  transmi.><sioii  with  no  distortion  or  lo.><ses. 

Common  battery  switchboards  manufactured  accordinir  to  Sifrnal  Corps  sjieciti- 
cations  are  furnished  in  three  sizes  acconunodatin^r  a  maximum  of  2<M)  lines.  100 
lines,  or  50  lines,  respectively,  the  actual  c(iuipment  in  either  case  deixMidin;: 
upon  the  needs  of  the  installation  to  which  it  pertains. 

The  three  sizes  are  similar  in  arranirement  of  parts,  in  operation,  and  in 
wiring.  A  description  of  the  50-liiie  size  therefore  applies  to  all.  This  switch- 
40581 "— 17 15  1-19) 


10  Signal  Corps  Manual  No.  3. — Chapter  6. 

board  is  shown  in  figure  6-6,  and  tlie  protector  cabinet  mentioned  in  first  part 
of  this  chapter  is  sliown  in  figures  6-7  and  6-S. 

In  figure  6-S  the  Cook  self-soldering  lieat  coil  and  protector  is  shown,  and  in 
figure  6-9  the  Western  Electric  heat  coil  and  protector  is  shown. 

The  cabinet  of  this  switchboard  is  built  of  oak  and  provided  with  an  uppei- 
and  lower  rear  door,  a  front  panel,  a  foot  rail,  and  is  designed  to  acconunodate 
all  of  the  apparatus  necessary  for  the  operation  of  the  system,  except  the 
battery. 

In  addition  t<»  the  50  common  battery  lines,  this  switchboard  i>rovides  a 
mounting  for  5  magneto  call  lines  for  long-distance  operation,  including  trunk 
connections. 

Ten  cord  circuits  are  provided.  The  conductors  of  the  cords  are  usually  of 
steel,  copper,  or  tinsel  strands.  The  keys  provide  for  ringing  on  the  calling 
cord  only.  This  arrangement  simplifies  the  wiring  and  eciuipment.  The  super- 
visory signal  also  acts  as  a  retardation  coil,  through  which  the  battery  is  fed  to 
the  coil  circuits.    This  signal,  like  the  line  signal,  shows  in  the  form  of  a  target. 

The  supervisory  signal  operates  when  the  cord  is  in  use  and  clears  wht^n 
the  parties  hang  iip.  A  movement  of  the  user's  hook  up  or  down  operates  this 
signal. 

The  line  signal  is  thrown  wlien  the  calling  party  removes  his  receiver  from 
the  hook  and  is  restored  automatically  when  the  operator  inserts  the  answering 
plug. 

The  common  battery  is  bridged  on  the  line  through  the  supervisory  signals. 

The  operator's  circuit  has  a  standard  common  battery  induction  coil,  which 
is  connected  to  battery  through  a  retardation  coil,  and  has  a  condenser  bridged 
across  the  source  of  current  supply.  A  condenser  is  also  placed  in  the  sec- 
ondary circuit  to  prevent  a  flow  of  direct  current  when  the  listening  key  is 
thrown. 

The  breast  ti'ansnntter  or  suspended  type  transmitter  and  single-head  re- 
ceiver which  form  the  operator's  ecpiipment  are  connected  to  wing-nut  binding 
posts  in  cabinet  of  switchboard  by  means  of  suitable  cords.  Tlie  operator's 
transmitter  is  provided  with  a   cut-out  switch  suitably  designated. 

'{"lie  night-bell  cii'cuit  provides  a  relay  and  vibrating  bell  and  operates,  if 
desired,  whenever  a  call  is  received. 

The  circuits  of  this  switchboard  are  shown  in  tigure  6-10.  Reference  to 
this  figure  indicates  that  when  the  subscriber's  hook  Jl  is  up  current  flows 
from  the  battery  through  the  jack  contact  C  to  the  subscriber's  instnnneni, 
tiirough  the  transiintt«'r  and  iiKhiction  coil  back  to  Jack  contact  A',  and  thence 
tln-ough  line  signal  to  battery. 

When  the  answering  plug  is  inserted  in  the  jack  •/  the  line  signal  is  cut  oil" 
and  falls  buck.  Current  now  Hows  to  the  user's  instrument  through  one 
winding  of  the  supervisory  signal  N,  through  c(mtii<'ls  of  key  Ix.  through  cord 
to  tip  of  ;ins\vering  T)lug,  tiirough  jack,  retiu'iiing  to  the  battery  through  lli(> 
odiei-  side  of  the  jack,  cord,  and  key  and  the  olliei'  winding  of  the  super- 
visory signal.  The  operator  depresses  listening  key  J\,  and  the  user's  voice 
<  urrents  flow  into  the  re^-eiver  circuit  at  the  switchboard.  The  calling  cord 
of  the  same  pjiir  as  the  miswering  cord  just  used  is  now  inserted  in  the  jack 
corresponding  to  the  line  desired,  the  key  R  is  depressed,  th<>  generator  turned, 
and  the  connection  is  established.  As  .soon  as  the  pluLT  is  inscrteil  curi-enl  flow- 
ing through  the  supervisory  signal  shows  "busy"  until  bolii  p.-ii'ties  hang  up 
(heir  receivers.  Should  eilliiT  parly  desire  to  nllract  central's  attention  a 
movement  of  the  switch  hook  will  cause  this  sigiud  to  flutter. 


Post  Telephone  Systems. — Chapter  6. 


11 


^J^f4>*^ /Y.41^ 


1 


FTT 


h 


Podahttf  p/^e 


!  ••-!. 


.1  . 


FRONT   VIEW   OF  DOOR 


SECTION   OF  DOOR 


■ 

-* 

, 

— 

f- 

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■p- 

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b 

FRONT  VIEW  OF  CABINET 
WITH  DOOfI  REMOVED     I 


SECTION 


ARRtST^  CiffNET 
KSXKtiOXIK 


NAME    PLATE 

Scale  ^if\*>l  in. 


Fig.  6-7.— SWITCHBOARD,  TELEPHONE.   PROTECTOR  CABINET. 


Part 
No. 


Name. 


Heference 
No. 


Cabinet  only 

Gla.'^s  for  door 

Door,  front 

Door,  back 

Panel  fuse  complete 

Slate  for  fu>e  panel 

.Screws  for  mounting 

Angles  for  mounting,  large. 
Angles  for  moimting,  small. 

Fuse,  baby,  3-ampere 

Fiase,  telephone,  j-ampere . . 


(221) 


12 


Signal  Corps  Manual  No.  3. — Chapter  6 


2        No8  LINE  PROTECTOR 

AND 

L-3  DISTRIBUTINO  FRAME 


Fig.  6-8.— SWITCHBOARD,   TELEPHONE,    COOK    PROTECTOR,    DETAILS. 


Part 
Xo. 


Name. 


Arrester,  complete,  without  heat  coil. 

Arrester  mountirifr 

Bolt  and  nut 

Carbons,  pairs 

Coil,  heat 

Mica 


Spacer 

Spring,  arrester,  rinht-hand 

Spring,  arrest pr,  left-hand 

Spring',  line,  ri^hl  -hand 

Spring',  line,  left-liand 

Terminal,  cross-connect iuK,  small •. 

Terminal,  cross-connectin;;,  large 

Terminals,  cross-connecting,  set  of  20,  with  mounting. 


Relerence 

No. 


Fig.  6-9.— SWITCHBOARD,    TELEPHONE,    WESTERN    ELECTRIC    PROTECTOR,    DETAILS 


Post  Telephone  Systems.— Chapter  6. 


i:; 


The  night-bell  circuit  of  this  central  enertry  switclihonnl  is  shown  in  figure 
0-11.     It  will  ho  soon  tlwit  wlicii  tlic  visual  siLriial  niicratt's  a  curnMit  will  How 

ZZ^3 r-^r — 


Calling  9r  Frvt  Cm/ 


==^1^ 


zT^yy. 


t:-\\ 


f 


I — VWWWW- 
( — ^AAV/W— 


~»«W«r- 


oo«^ 


I      Hl|l|l|lll|l|l|l|l[lllll|l|l|^^ 


Lisli^ 


^  TrarumitLtr  switz 

■o<^ 


fusta  iit 


Fig.  6-10.— SWITCHBOARD,   TELEPHONE,    VISUAL,    CIRCUITS. 

from  the  common  battery  thi-ough  the  contact  of  the  night-boll  key  A',  thence 
thnmgh  the  rolav.  thence  through  the  contact  of  the  arniat\n-o  <if  the  signal, 


i 

W^ttttttnth 

J/'  itHnflt)^' 

G 

O        <j 

)) — 

1^^^ 

f'l 

0 J 

^ — ^11 — ' 

Hi- 

c 

Fig.  6-11.— SWITCHBOARD,   TELEPHONE.    VISUAL.    NIGHT-BELL   CIRCUIT. 

returning  to  the  battery.    The  operation  of  the  relay,  however.  iK'rmits  current 
to  flow  from  the  tlry  cells  I)  through  the  right -han.l  contact  of  tiie  key  K,  theuc-e 


('2-2-Ai 


14 


Signal  Corps  Manual  No.  3. — Chapter  6. 


tliroush  the  bell  and  back  to  the  battery  D.  When  the  niasneto  drop  operates, 
current  will  flow  from  the  battery  D  through  the  right-hand  contact  of  the  key 
K,  through  the  armature  contact  of  the  magneto  drop  M,  through  the  bell  B, 
returning  to  the  battery  7). 


Pi/ot  lamp,  redcap 
)30v. 


Night  bell, 
for  all  positions 

lO      0| 


One  relay ^  for  each 
operators  position 


|f^0^|_ 


c5 


Night  bell 
3mtch 


Rus  bars  on  fuse  panel 


4 


Pilot  lamp,  redcap 


\\^  lOohms^W 


rS 


n 


+1 — ?i 


Bus  bars  on  fuse  panel 
NIGHT-BELL  CIRCUIT. 


fit 
Dry  battery 

Fig.  6-12.— SWITCHBOARD,   TELEPHONE,   200-LINE, 

It  will  be  noted  that  with  the  visual  signal  a  relay  is  utilized  to  close  the 
night-bell  circuit.  The  reason  for  this  is  that  the  contacts  of  the  visual  signal 
are  of  a  delicate  nature  and  it  is  advisable  to  reduce  to  a  mininunn  the  current 
strength  broken  at  these  contacts. 


Cenerator  Call  Drop 


Fig.    6    13.— SWITCHBOARD,   TELEPHONE,   200-LINE,    GENERATOR    DROP  CIRCUIT. 

(224) 


Post  Telephone  Systems. — Chapter  6. 


15 


With  tlio  200-lin('  size  only,  tlu'  iii;,'lit-lK'll  circuit  is  ;is  shown  in  fiffiirp  0-12. 
Witli  tiiis  size,  a  small  .SO-voIt  pilot  lamp  is  lij^hted  by  means  of  a  relay  whenever 
any  one  (»f  the  line  sijinals  is  operated. 

Where  tlie  lenjith  or  resistance  of  lines  make  common  hattery  si^rnalin;; 
impracticable,  or  where  the  line  is  contained  in  submarine  cable  u  con.siderable 
distance,  one  of  tlie  generator  call  drops  is  brought  into  service. 

Figure  6-13  shows  approved  metliod  of  wiring  in  a  circuit  of  this  l^ind  wliere 
a  telephone  instrument  is  installed  at  the  distant  station. 

It  will  be  noted  that  the  telephone  connected  to  suc-h  a  circuit  must  be  of 
l(»cal  battery  or  composite  type,  and  that  the  line  between  switchboard  and  sub- 
station is  not  connected  to  battery  leads  at  either  end.  In  other  words,  tlie  line 
is  "dead,"  except  when  calling  or  talking  is  in  progress,  and  then  the  currents 
imposed  upon  the  line  are  alternating  or  pulsating.  This  condition  is  highly 
desirable  where  line  is  contained  in  submarine  cable,  especially  if  tlie  insulation 
of  cable  be  rubber  compound. 


fUaarsi biack.   One  forcfCty  ten  hna  J«c*e 


m 


)  eo  ID  eo  50  ■- 


0  o  o  p  o 


BlQiJf.  f>v  for  ctvjy  SOjitcAs 


.Tx: 


^'W'I>I'I'I'I'I'^T+ 


Amntrinq  cord 


li\ 


mm 


Jack^ 


One  bdlfaraUpaitJons 


To  magnito  drops 


Jcpiiotlgmp 
0^200  line, 
boanionhf 


OrunQC->rf»t£ 


LINE  SIGNALS 


PuncJitngs 


m^ll 


Dry  battery 


To  ope/aton  urcutt  -  D/urrrry  666 L 


i- 


3: 


LAMP    SIGNALS 


To  nn^rn^  drxMit. 
Dntrng  eaeL 


Fig.  6-14.— SWITCHBOARD,    TELEPHONE,    VISUAL    LINE    SIGNAL,    LAMP    SUPERVISORY 

CORD   CIRCUIT. 

The  condensers  in  series  with  each  line  ar  the  switcliboanl  prevent  the 
common  battery  coming  in  direct  contact  with  the  line,  while  the  alternating 
and  ptilsating  currents  employed  in  calling  and  talking  are  not  prevented 
from  reaching  line  by  the  condensers. 

What  has  just  been  stated  of  the  switchboards  equipped  with  "  visual 
signal  for  line  signal  and  vistial  signal  for  supervisory  signal  "  is  true  of  the 
switchboard  having  "  visual  signal  for  line  signal  and  lamp  signal  for  super- 
visory signal,"  except  that  instead  of  having  visual  signals  in  the  cord  cir- 
cuits a  small  30-volt  electric  lamp  with  colored  caps  (usually  red),  both  of 
which  are  mounted  on  key  shelf,  are  supplied. 

(22b) 


16 


Signal  Corps  Manual  No.  3. — Chapter  6. 


By  means  of  :i  relay  for  each  cord,  when  tlie  operator  phiss  into  a  jack, 
the  hnnp  for  tliat  particnhir  cord  lights  an«l  is  extinjiuished  when  party  called 
removes  receiver  from  hook.  When  either  of  tlie  two  parlies  coniu'cted  by 
means  of  the  telephone  switchboard  hang  receiver  on  hook,  the  relay  asso- 
ciated with  the  particular  cord  used  for  connection  is  operated.  This  in  turn 
lights  the  small  lamp  associated  with  that  particular  cord,  and  the  operator 
is  thereby  notified  that  line  is  not  in  use. 

This  type  of  switchboard  is  now  furnished  for  the  ."(),  100,  and  1200  line 
size. 

Figure  6-14  shows  the  cord  circuit.  The  other  circuits  of  the  switcbboai-d 
are  identical  with  those  of  the  switchl)oard  previously  described. 


LAMP    SIGNALS    FOR    LINE    SIGNALS    AND    LAMP    SIGNALS    FOR    SUPERVISORY     SIGNALS. 

For  all  telephone  switchboards  having  a  line  capacity  exceeding  200,  lamp 
signals  for  both  line  and  supervision  are  supplied.  Where  the  line  capacity 
of  tlie  switchboard  is  between  100  and  400,  it  is  constructed  for  operation  by 
two  operators  (two-position  switchboard),  although  provision  is  made  whereby 
one  operator  may  use  eitlier  operator's  set  for  operation  of  tlie  wliole  switch- 
board by  merely  closing  a  switch.  Tliis  arrangement  is  made  in  order  that  one 
man  only  need  be  kept  on  duty  during  period  tliat  few  calls  are  made. 

The  only  size  above  300-line  capacity  that  has  been  furnished  by  the  Signal 
Corps  is  600-line.  This  switchboard  is  a  three-position  (three  operators) 
multiple  switchboard  of  commercial  type.  The  two  outside  positions  are  mul- 
tipled.  This  means  that  either  of  the  two  outside  operators  may  plug  into 
jacks  connected  to  each  of  the  lines  terminating  at  the  other's  position.  These 
jacks   are  mounted   directly   above   the   regular   line  jaclcs.     The  operator  at 


RiMGiNG    CIRCUIT 


Fig.  6-15.— SWITCHBOARD,   TELEPHONE,    LAMP    LINE   AND    LAMP   SUPERVISORY 

NALS,   CIRCUITS. 
(1-20) 


SIG- 


Post  Telephone  Systems. — Chapter  6. 


17 


central  position  is  alile  to  reach  tlie  line  jacks  of  either  of  the  other  positions, 
coiisejpiently  the  niultiiile  jacks  are  not  fiirnislied   for  liiis  jiosition. 

The  princi[)al  cii-cnits  of  all  teieplione  s\vI1(1iIiomi-(Is  ahovc  I  he  'JiKi-liiif  size 
furnishi'il  by  the  Sitrnal  C\irps  are  similar,  anil  are  shown  in  tijrnrcs  C  1."i  and 
C-IG,  while  by  referring  to  figure  6-17,  u  view  of  a  3(X)-line  switchboar<l  with  dis- 
tribiiting  frame  installed  about  S  feet  from  switchboard  may  be  seen.  Figure  G-3 
shows  this  same  distributing  frame  upon  which  are  mounted  strips  supporting 


e  lamp  No.  O 


^/W\      I  Pu^h  button  in 
Sj    U      \tirte  jocM  position 


TEST    CIRCUIT  IN    NO.    O     LINE  POSITION 

Fi?.  6-16.— SWITCHBOARD,   TELEPHONE,    LAMP   LINE   AND    LAMP   SUPERVISORY   SIG- 
NALS, TEST  CIRCUIT. 


Fig.  6-1  7. — raVv  I  i  k.  ri  bw«  rs  lj 


..^rHONE,    LAMP    LII,L    / 
NALS.   IN   OPERATION. 

(227) 


IS 


Signal  Corps  Manual  No.  3. — Chapter  6. 


metal  punchings  to  which  inconuiif;-  lines  are  terminated,  also  the  protectors 
previously  described  in  this  chapter.  The  cross-connecting  of  the  lines  to 
protectors  in  this  installation  was  accomplished  hy  usinji  i)othead  wire,  and 
tlie  switchboard  cables  from  protectors  to  switchboard  were  encased  in  an 
oak  runway,  supported  by  1  by  5  inch  iron  pieces. 

In  addition  to  tlie  equipment  herein  described  for  switchboards,  all  size.s 
above  the  200-line  size  are  usually  equipped  with  a  number  of  special  relays 
used  in  the  operation  of  lines  connected  to  the  common  battery  circuits  of 
commercial  exchanges.  It  must  be  borne  in  mind  that  in  making  such  a 
connection  the  common  battei*y  of  the  connnercial  exchange  is  connected  to 
the  line  which  is  connected  to  the  Signal  Corps  switchboard,  also  that  super- 
vision at  both  switchboards  must  be  maintained.  This  is  accomplished  by 
means  of  a  locking  relay  for  each  such  line  connected  to  Government  switch- 
board. 

Any  of  the  switchboard  cords  may  be  used  for  connection  with  jacks  asso- 
ciated with  these  relays.  The  circuits  usually  employed  with  these  locking 
relavs   aiv   shown   in   tigni-(>   0-18.     Tn   ti-aciiig   these   circuits   it   will    be   noted 


0     0     0     0  i 

3 

B.T^ 

B..^e.B   - 

+ 

0 

0     0  t 

GROUND 

bob bAR 

PILOT  LAMP 

1 ;          ^ 

^ 

-o\ 

..,«. 

f 

? 

1 7/7//,  I 


7J7/J  f/fff 


ra 


ZX2' 


Ofrt  &AITCR* 


Fig.  6-18.— SWITCHBOARD,   TELEPHONE,    LOCKING    RELAYS,    CIRCUITS. 

that  a  condenser  prevents  the  connnon  battery  of  the  commercial  exchange 
cdiiiplcting  a  circuit  through  connnon  l)a(tery  of  (Jovernment  exchange  when 
the  cord  plug  of  Government  exchange  is  inserted  in  trunk  jack.  Also,  that 
when  the  openitor  of  the  commercial  exchange  impresses  a  ringing  current 
upon  the  line  in  the  usual  maimer,  one  winding  of  the  locking  relay  is  in 
the  circuit.  This  causes  armature  of  locking  relay  to  vibrate,  due  to  ringing 
current  being  alternating  in  chara<'ter.  A  slight  vibi'atory  movement  of  the 
armature  closes  a  coiitact,  wliicii  in  turn  closes  a  circuit  consisting  of  the  other 
winding  of  relay  in  i)ai'allel  with  tnnd<-line  lamp  and  pilot  relay  in  series 
and  the  combination  In  series  circuit  with  the  connnon  battery  of  Government 
exchange.  The  trunk-line  lamp  remains  lighted  when  connnercial  operator 
ceases  to  ring,  due  to  armature  of  locking  relay  beinj;  held  in  contact  by  the 
direct  current. 

When  Goveriniient  oi»erator  withdraws  cord  plug  from  jack,  upper  contact 
of  jack  is  broken,  and  the  sujiervisory  lamj)  of  c<»nnnercial  switchboard  is 
thereby  lighted. 

For  Government  operator  to  call  commercial  operator,  it  is  diily  ncu-essary 
t«)  insert  cord  plug  in  one  of  the  trunk  jacks.  This  operation  signals  the  com- 
mercial oi»erator  in  exactly  the  same  manner  as  removing  receiver  from  hook 
of  a  telej)hone. 

(228) 


Post  TelepKone  Systems. — Chapter  6. 


19 


(229) 


20 


Signal  Corps  Manual  No.  3. — Chapter  6. 


Supervision  at  Government  switchboard  is  aecomplislied  by  niean«  of  super- 
visory lamp  in  one  side  only  of  cord  circiut. 

Figure  6-19  shows  the  principal  circuits  in  one  diaurain  of  laiiiii-liiic  signals 
and  lamp-supervisory  signals  switchboard. 


FRONT  VIEW  VERTICAL  SECTION 

Fig.  6-20.— SWITCHBOARD,   TELEPHONE,    LOCAL   BATTERY  TYPE,    15    LINE. 

CJ.-'.O) 


Post  Telephone  Systems. — Chapter  6. 


21 


MAGNETO    SWITt'IIBOAKD.S     (LOCAL    BATTEKV    TYl'K). 

MaRiiPto  s\vitcli!)(>;inls,  or  lociil  battery  type,  are  usually  provided  for  small 
l)osts  and  for  temporary  iustallati(»ns  where  conditious  at  post  do  not  warrant 
ttie  installation  of  the  standai'd  couuuon  battery  system. 

The  operation  and  mainti'njince  of  such  systems  is  nmiparalively  sinii»le. 
They  may  consist  of  a  mininnim  of  12  telephones. 

For  the  small  installations,  the  Siirnal  Corps  has  applie<l  a  l."»-droii  suii.li- 
board.  These  were  made  under  Siirnal  Co/ps  speciticatious  and  are  shown  in 
figures  6-20  and  fi-21. 


Night  bell 


yOrvceJ/i 


Drop 


n^5 


S^ 


Jack 
Drop 


Jack 


Mason  or^csie.' 

I O    Q-SO 

O '         I 


Cords  should  conned:,  in  fast£ners  Up  to  bp  and  skeve  to  sk^ve, 
ground  lines  coming  in  on  long  c- '  ■■'•i 

Fig.   6-21.— SWITCHBOARD.   TELEPHONE,    LOCAL   BATTERY    TYPE,    15    LINE,    CIRCUITS. 

This  .switchboard  consists  of  a  neat  oak  cabinet  accommodating!  !">  combined 
drops  and  .jacks.  5  pairs  of  cords  with  clearinj:-out  drops,  and  "i  jrroupint:  jacks. 
The  operator  is  provided  with  a  sinj:le  head  receiver,  and  the  switchboard  has 
an  adjustable  operator's  transmitter  and  the  usual   night-bell   circuit. 


(231) 


22  Signal  Corps  Manual  No.  3. — Chapter  6. 

An  arrester  cabinet  providing  for  an  ultimate  installation  of  20  Mason  or 
similar  lightning  arresters  with  fuses  accompanies  this  switchboard,  sufficient 
cable  being  provided  to  reach  from  the  usual  location  of  the  switchboard  to 
the  arrester  cabinet  usually  installed  on  the  wall  at  the  rear  of  the  switch- 
board.    The  operator's  circuit  is  usually  operated  by  4  gravity  cells. 

The  circuit  is  as  follows   (fig.  6-21)  : 

The  calling  party  signals  central  by  a  magneto  call,  throwing  the  line  drop. 
The  operator  inserts  an  answering  plug  (opening  the  drop  circuit  and  at  the 
same  time  automatically  restoring  drop  shutter)  and  places  key  into  talking 
position. 

The  connection  is  established  by  inserting  the  calling  plug  into  desired  line 
jack.  The  conversation  completed,  the  usual  ring  off  throws  the  clearing  out 
drop,  signaling  the  operator  to  disconnect.  All  instruments  operating  througli 
this  board  are  on  local  battery. 

(Jroupiug  jacks  are  provided  to  connect  several  lines  together  by  placing 
answering  plug  in  line  jack  and  calling  plug  in  grouping  jack. 

The  operator's  circuit  is  of  the  simple  induction  principle  used  in  ordinary 
telephones. 

These  boards  are  wired  for  15-line  di-ops  only,  and  it  is  not  practicable  to 
increase  their  line  capacity  without  sending  them  to  some  Signal  Corps  supply 
depot.     It  is  not  probable  that  any  more  of  this  type  of  board  will  be  issued. 

This  board  should  have  four  cells  of  gravity  battery,  size  5  by  7,  for  the 
operator's  telephone,  as  this  telephone  has  normally  a  closed  circuit,  and  there- 
fore dry  cells  or  any  other  type  of  open-circuit  battery  should  not  be  used 
unless  a  cut-out  switch  is  provided. 

50-LINE  MAtlNETO  SWITCHBOARD. 

For  local-biittery  telephone  systems  of  more  than  15  antl  not  exceeding  50 
lines  the  Signal  Corps  has  in  service  a  number  of  local-battery  magneto  switch- 
boards. These  boards  have  an  ultimate  capacity  of  50  lines  and  are  so  wired. 
They  are  supplied  to  posts  with  20,  30,  40,  or  50  drops  installed,  depending  upon 
the  number  of  telephone  lines  required.  In  this  board  the  operator's  telephone 
is  nominally  a  closed  circuit,  and  four  cells  of  gravity  battery,  5  by  7  size, 
should  i)e  used. 

Additiouiil  drops  and  jacks  can  be  supplied  for  these  boards  and  installed 
with  facility  at  any  time  to  increase  the  cai)acity  up  to  50  lines,  as  the  necessary 
wiring  is  already  complete. 

This  switchboard  is  a  stock  article  of  conniiercial  use.  Figures  6-22  and 
(t-'2'.\  Illustrate  the  appearance  and  circuits  of  this  equipment. 

It  has  an  oak  cabinet  and  is  jjrovided  with  hand  generator,  5  pairs  of 
cords  with  listening  and  double  ringing  keys,  bridged  supervisory  magneto  drop 
sigiKils.  liiiiid  generator  and  buzzer  which  can  be  cut  into  the  ringing  circuit  as 
dcsirt'd  for  lest,  two  keys  for  these  various  ringing  circuits,  and  operator's 
Iransniil  tfi-  and  IicjkI  rcccivci-  complete. 

FigUH'  ()-2;{  shows  the  circuit  of  this  s\\  ilchboard.  It  will  be  seen  that  the 
line  signal  is  bridged  across  the  line  jack  and  is  cut  off  from  both  sides  of 
the  line  when  the  plug  is  inserted. 

The  cord  circuit  is  the  usual  circuit  with  hridgiMl  supervisory  signal,  which 
is  rung  dr>wn  by  (lie  stations  coiuiectcil  for  ciill  wIhmi  tlicy  ring  off  :it  end  of 
the  conversjition. 

Tlic  rcil  keys  on  I  he  left-hand  side  of  the  keyboard  arc  those  shown  in  the 
ringing  circuit.  P.y  throwing  the  key  it  is  possible  to  cut  the  buzzer  in  series 
with  the  ringing  circuit.     This  is  desirable  when  a  line  indicates  a  defective 


Post  Telephone  Systems.  ^Chapter  6. 


23 


condition.  The  condition  of  tiie  line  in  regard  to  open  or  short-circuited  wires 
will  be  indicated  by  the  action  of  the  buzzer,  its  loudness  being  determined 
by  the  resistance  in  the  line  for  a  uniform  rate  of  turning  of  the  hand  gen- 
erator. On  some  of  the  boards  the  key  provided  for  switching  the  ringing 
circuit  from  power  to  hand  generator,  and  vice  versa,  is  so  wired  that  it  is 


Fig.  6-22.      SWITCHBOARD,    TELEPHONE.    LOCAL   BATTERY   TYPE.    50   LINE. 

necessary  when  using  the  hand  geuerat«»r  to  throw  the  key  over  from  the 
normal  position.  Inasmuch  as  power-i'inging  current  for  these  boards  is  seldom 
available  and  is  not  provided,  this  key  should  be  rewired  so  that  the  hand 
generator  is  connected  directly  into  the  ringing  circuit  while  the  key  is  in  its 
normal  position. 


(233) 


24 


Signal  Corps  Manual  No.  3. — Chapter  6. 


If  power  ciirivnt  should  he  avaihihle.  it  sliouhl  he  connected  to  the  si)rinffs 
marked  "  generator.  Xos.  1  and  2."  on  the  terminal  board  of  the  switchboard 
and  the  Ivey  circuit  retained  in  its  present  form. 


Ans Orange 


Green 


Call 


White 
Plug  Ooublc  ^i'\Qirio\  Apy 


White 
UsteninqKGy 


Plug 


,'1    Bh.r     p^ 


/d  ng'ing Buzzer     Night  bell 
6h.Ctq  Hey.  key 


o — , 
Supervisory  drop 


No.  S>4  Key 

Ringing  R>Y^er  H^ 


^^^WJ' 


Line  drop 


*— AWWA^ 


P^iver  clips 


3-4    Trans  battery  ^\  CiAfund 

5-6   Night  bell  battery        ^\  — ^ 
1-8  Telcplionc  top 


Fig.  6-23.— SWITCHBOARD,    TELEPHONE,    LOCAL    BATTERY   TYPE,    50-LINE,  CIRCUITS. 

7l  lias  also  been  found  in  some  cases  that  the  .generator  armatures  of  these 
switcliboai'ds  contiinie  to  revolve  after  a  call  has  l>(>en  made,  thus  unscrewiu.ii 
the  genei'ator  handle  Iroui  the  drivin.u  shaft.  To  avoid  this  a  liigh  resistance 
will  be  prox  ided  to  be  bridged  across  ternnnals  X  and  Y  of  tln'  hand  ,i:tMierator 
shown  in  tigure  6-23,  in  order  to  furinsh  a  slight  load  for  (he  gt'uerator  and 
cause  the  armature  to  stop  as  soon  as  the  .generator  handle  is  released.  A 
requisition  should  be  made  for  these  resistances  wherever  their  use  is  con- 
sidered to  be  of  advantage. 


i'i-.A) 


Post  Telephone  Systems. — Chapter  6. 


25 


COUKI.ICSS    SWlTCIinO.UM). 

Figures  6-24  and  6-25  sIkiw  a  si^ecial  cordloss  magneto  type  switclihoard 
designed  to  meet  special  conditions  tliat  ol)tained  in  connection  witli  tiie  in- 
stallation of  a  post  telephone  system  at  the  Army  Remount  Depot  near  Front 
Royal,  Va. 

As  it  was  impracticable  to  furnish  a  switchboard  operator  in  this  instance, 
the  switchboard  is  operated  by  a  clerk  during  ofTice  hours  and  a  watchman  at 
other  times.  The  switchboard  is  supported  by  a  table  placed  beside  the  clerk's 
desk. 


Fig.  6-24.— SWITCHBOARD,   TELEPHONE,    LOCAL    BATTERY,   CORDLESS. 

It  is  only  necessary  to  operate  keys  to  obtain  desired  cross  connections. 
The  switchboard  is  of  2U-line  capacity  and.  as  shown  in  the  figures,  the 
operator's  set  consists  of  an  ordinary  telephone  desk  stand  with  hand  receiver. 
Figure  6-26  is  a  circuit  diagram  of  the  switchboard. 

By  depressing  a  locking  key  (marked  "  iV.l  "  in  figure  6-24)  a  small  bu/zer 
contained  in  the  cabinet  is  so  connected  in  circuit  that  the  buzzer  will  operate 
when  a  call  is  received.  By  depressing  an  additional  locking  key  (marked 
"EXT"  in  fig.  6-24)  the  buzzer  is  cut  out  of  circuit  and  a  loud  ringing 
water-tight  bell,  located  outside  of  the  administration  building,  is  made  to 
operate  when  a  call  is  received.  The  latter  is  used  to  notify  the  watchman, 
who  is  required  to  make  regular  rounds  of  the  post  at  night. 

The  operator's  circuit  and  bell  and  buzzer  alarm  are  operated  by  means  ol 
No.  6  reserve  dry  cells  contained  in  the  cabinet  of  the  switchboard. 


46581°— 17- 


(235) 


26 


Signal  Corps  Manual  No.  3.— Chapter  6. 


Fig.  6-25.— SWITCHBOARD.  TELEPHONE,    LOCAL    BATTERY,   CORDLESS,   OPEN. 
INSTALLATION    OF   TELEPHONE    SWITCHBOARDS. 

Care  should  be  taken  in  unpacking  switcliboard  apparatus  so  that  it  will 
not  be  injured.  Different  manufacturers  use  various  methods  of  packing  ma- 
terial SO  it  will  not  be  injured  in  transit.  Braces  will  be  found  in  the  packing 
which  must  be  removed  as  the  material  is  taken  out.  If  the  apparatus  is 
found  to  be  in  an  injured  condition,  note  should  immediately  be  made  of  this 
fact,  witnesses  called  in  for  verification,  and  a  report  immediately  submitted 
so  that  proper  action  may  be  taken. 


._:.i..t^ 4- — ij        I     „Ki  ■        w  1 1 1 


Fig.  6-26.— SWITCHBOARD,   TELEPHONE,    LOCAL   BATTERY,   CORDLESS,   CIRCUITS. 


Post  Telephone  Systems. — Chapter  6.  27 

The  cord  wci^ilits  an*  usually  lied  up  and  fasttMU'd.  Uclays  which  hnw  metal 
covers  are  usually  tilled  with  paper  so  tliat  the  relay  will  not  be  injured  by 
shaking.  The  apparatus  should  be  given  a  thorough  cleaning  and  cleared  with 
a  bellows.  Care  should  be  taken  that  not  any  of  the  extra  parts  are  thrown 
away  with  the  excelsior  or  other  packing  materials.  All  fuses  should  be 
tested  and  care  taken  with  the  remainder  of  the  apparatus. 

Blue  prints  and  instructions  usually  accompany  each  switchboard,  and  these 
should  be  followed  in  the  erection  of  the  material. 

Telephone  switchboai'ds  for  post  systems  are  usually  installed  in  the  ad- 
ministration building,  as  stated  in  General  Orders,  No.  .j,  War  Department, 
]J)i;i.  4n  selecting  the  location  consideration  should  be  given  the  following 
requirements  in  order  tt)  insure  good  telephone  service:  The  room  .selected 
should  be  quiet  and  free  from  intruders,  so  that  the  operator's  attention  may 
not  be  diverted  from  his  dutie.s.  Sleeping  quarters  for  the  operators  are  also 
desirable  if  all-night  service  is  contemitlated.  The  necessity  of  rvuming  the 
lead-covered  cables  from  the  switchboard  room  to  the  outside  circ\iits  sbouhl 
also  be  remembered,  as  the  protector  equipment  must  always  be  located  in  the 
same  room  with  the  switchboard. 

The  switchboard  shoui<l  be  located  so  that  the  light  falls  on  the  front  of  the 
board  and  so  that  the  operator  is  not  compelled  to,  face  a  strong  light.  The 
back  of  the  boards  that  ai'e  not  built  for  installation  on  the  wall  and  hinged  to 
swing  out  for  inspection  should  never  be  nearer  than  2  feet  to  the  wall  so  that 
the  wiring  is  always  accessible  for  inspection. 

Switchboard  cable  is  invariably  used  for  connecting  appropriate  line  termi- 
nals in  switchboards  with  associated  protectors  in  protector  cabinet  or  on  dis- 
tributing frames. 

The  standard  Signal  Corps  switchboard  cable  consists  of  20  twisted  pairs  of 
conductors,  with  one  spare  pair  and  one  odd  wire.  The  conductors  are  of  soft 
copper  wire,  25.3  mils  diameter,  insulated  by  two  wi-appings  of  silk  applied 
spirally  in  reverse  directions,  and  a  wrapping  of  cotton.  The  twisted  pairs  are 
assembled,  imi)regnated  with  beeswax  and  wrapped  with  cotton,  then  a  wraj)- 
ping  of  paper,  a  layer  of  tin  or  lead  foil  wrapped  spirally  and  lapped,  another 
wrapping  of  heavy  paper,  a  wrapping  of  cotton,  and  a  heavy,  close  braid  of 
cotton  treated  with  fireproof  slate-colored  paint.  The  cotton  wrapping  of  one 
conductor  of  each  pair  is  white,  and  the  other  a  color  conforming  to  table 
which  follows.  In  connecting  this  cable,  the  following  arrangement  of  colors 
should  always  be  adhered  to.  Under  no  conditions  should  any  other  sequence 
of  colors  be  followed,  as  this  arrangement  is  standard,  and  is  a  very  important 
guide  to  the  repair  man  who  maintains  the  system. 

SWITCHBOARD  CABLE.  fOl.OK  SC  HKME. 

First   pair Blue.  White. 

Second    pair Orange.  White. 

Third  pair Green.  White. 

Fourth    pair Brown.  White. 

Fifth  pair Slate.  White. 

Sixth  pair -■ Blue-white.  White. 

Seventh    pair Blue-orange.  White. 

Eighth    pair Blue-green.  White. 

Ninth  pair Hiue-browu.  White. 

Tenth    pair Blue-slate.  White. 

Eleventh  pair Orange-white.  White. 

Twelfth    pair_,— _, Orange-green.  White. 

(237) 


28  Signal  Corps  Manual  No.  3. — Chapter  6. 

Thirteenth  pair OraniLie-hrown.  Wliite, 

Fourteenth    pair Orange-shite.  White. 

Fifteenth   pair ^ Green-white.  White. 

Sixteenth  pair Green-brown.  White. 

Seventeenth    pair Green-slate.  White. 

Eighteenth  pair Brown-white.  White. 

Nineteenth  pair Brown-shite.  White. 

Twentieth    pair Slate-white.  White. 

Ordinarily  switchboards  are  not  provided  with  the  switchboartl  cables  con- 
nected, and  requisitions  should  specify  the  length  of  cable  required  to  reach 
the  protector  cabinet.  The  line  cable  should  be  neatly  formed  as  directed  in 
a  later  paragraph  and  carefully  soUlered  to  the  line  terminals,  care  being 
taken  to  make  well-tinned  joints,  as  often  the  resin  deposited  when  soldering 
is  mistaken  for  solder,  and  also  that  corresponding  wires  of  the  line  cable 
pairs  are  connected  to  similar  sides  of  the  switdiboni-d  lines.  In  connecting 
the  line  cables  to  the  protector  cabinet  the  method  adopled  must  be  such  that 
there  will  be  no  likelihood  of  the  cable  becoming  wet  wlien  I  be  lloor  is  scrubbed 
or  in  any  other  way.  For  this  reason,  if  the  cable  is  run  luider  tlu'  tloor, 
provision  should  be  made  for  tliis  contingency,  as  the  line  cables  usmdly  ju'o- 
vided  and  a<l(ipted  for  this  work  have  no  particular  moisture-resisting  properties. 

The  outside  line  cables  should  be  potlieaded  above  the  tloor,  the  wiped  joint 
resting  on  the  floor  and  taking  up  any  strain  tliat  might  othex'wise  be  upon 
the  connections  in  the  terminal  or  protector  cabinet.  For  magneto  switch- 
boards which  have  separate  protector  cabinets  installed  on  the  wall  and  apart 
from  the  switchboard  proper,  the  top  of  the  pothead  sleeve  should  terminate 
just  inside  the  bottom  of  the  cabinet  and  pothead  should  be  clamped  securely 
to  blocks  on  wall  and  protected  from  injury. 

Inside  the  cabinet  the  wires  should  be  foi-med  ami  laced  and  iiermaiiently 
held  in  ])lacc  by  small  leather  strajis  so  tlint  Ibc  woi"k  js  permanent  in  every 
way. 


f 


mmti 


Fig.  6-27.— SWITCHBOARD,   TELEPHONE,    FORMING    CABLE   CONDUCTORS. 

All  telephone  switchboards  should  be  installed  in  a  i)ermanenl  manner  and 
the  schenu;  of  wiring  followed  which  will  nnnimize  trouble  in  maintenance 
work. 

The  telei)hone  switchboard  should  always  be  bolted  to  the  floor  so  that  it 
will  be  held  itermanenlly  in  lis  ixisition  and  also  because  the  boards  are  usually 
top-heavy  and  not  intended  to  stand  uiisui»ported. 

The  nt'cessary  r-oi-d.  magneto,  line,  and  biis-baf  condensers  are  installed  at 
the  rear  of  the  <-entral  energy  switchboards.  A  diagram  showing  the  arrange- 
ment (tf  Ibis  jii)i»aralus  is  iirovided  with  the  dilferent  brtards.  Forms  should  be 
made  for  these  comiecti(nis,  allowing  as  nuich  slack  as  possible  Coi-  emergencies. 

In  wiring  thntugb  the  lloors  jtorcelain  lubes  of  ami>le  size  shoidd  be  made 
U.se  of,  and  gr<'at  ('are  should  be  taUen   in  all   the  cabling  (hat  no  damage  may 


Post  Telephone  Systems. — Chapter  6. 


29 


result  to  the  installation  Iroiii  carelessness  on  (lif  |iarl  of  the  occupants  of 
till'  liuildiii;,"  ill  wliifh  the  hoard  is  installed. 

Wlicic  cnlilc  luriiis  are  reciuired,  and  |»arti<idail.v  at  tlir  ends  dl'  (he  cahlc 
wliicli  is  to  he  u.'^ed  to  eoniiect  tiic  liiic  wires  lo  liic  .inH'stcr  strips,  ("liilf  fitniis 
sliduld  lie  made  up  as  follows: 

After  the  eahle  is  laid  in  its  iiernianent  position  its  free  ends  siiall  he  laid 
parallel  to  terminals  to  which  it  is  to  he  attached.  The  end  of  the  cable 
should  extend  a  distance  X  (tig.  6-27)  heyond  the  top  clip  of  the  strip.  At  the 
hottom  of  the  strip  a  butt  niai*k  should  be  made  about  an  inch  lielow  the  lower- 
most clip,  to  which  this  cable  is  to  be  attached. 

The  outer  covering  of  the  cables  should  then  he  removed  from  the  butt  mark. 
so  as  to  expose  the  twisted  pairs.    This  is  accomiilished  liy  the  use  of  a  sharp 


Fig.  6-28.— SWITCHBOARD,   TELEPHONE,    FORMING   CABLE   CONDUCTORS. 

hnife,  being  careful  not  to  cut  the  insulation  of  the  wires.  The  knife  should  be 
held  in  a  slanting  dix'ection  to  the  cross  section  of  the  cable  in  this  operation. 
In  cutting  the  cable  around  the  butt  mark,  so  as  to  leave  a  clean  end.  care 
should  be  taken  not  to  cut  the  insulation  or  damage  the  wires.  All  iiinding 
strips  should  be  removed  with  the  sheath  from  the  cable. 

A  strij)  of  cotton  tape  one-half  of  an  inch  in   width  should  now  be  bound 
ti.iihtly  around  the  exposed  edges  of  the  cable  covering.    The  operation  of  biiid- 


•  CABLCCLAt'' 


^  TWISTCD  PWW  -  CONDUCTORS 


Fig.  6-29,  — SWITCHBOARD,  TELEPHONE,    FORMING   CABLE   CONDUCTORS, 

ing  the  cable  at  this  point  is  known  as  "  butting  "  and  should  proceed  as  shown 
in  figure  G-28.  The  tape  is  first  looped,  and  then  its  long  end  is  wound  around 
the  cable  four  or  five  times  and  threaded  throu.gh  the  loop  which  was  tirst 
formed.  The  end  B  is  then  drawn  under  the  turns  by  pulling  the  end  .4  and 
closing  the  loop.    Next,  the  loose  ends  :ire  cut  away  and  a  coating  of  shellac  is 


(239) 


30 


Signal  Corps  Manual  No.  3. — Chapter  6. 


applied,  completing  the  butt.  Tlie  exposed  twisted  pairs  of  the  standard 
switchboard  cable  should  now  be  put  in  boiling  yellow  beeswax  np  to  the  butt 
until  all  the  bubbles  disappear  from  the  liquid.  The  purpose  of  this  wax  is  to 
expel  all  moisture  and  improve  the  insulation  of  the  wires,  and  also  to  prevent 
the  braid  loosening  iip  while  the  form  is  being  completed.  All  siuiilus  wax 
should  be  gently  beaten  from  the  cable  with  a  stick  when  it  is  removed  from 
the  boiling  pan. 

The  cable  is  now  clamped  at  the  butt  lo  the  board,  as  shown  in  figure  6-29. 
and  each  pair  of  wires  is  selected  in  numerical  order,  according  to  the  color 
code,  dyed  in  the  insulation  of  the  conductor,  and  drawn  into  place  and 
fastened  around  each  successive  nail.  The  length  of  wire  allowed  between 
the  stem  of  the  cable  and  the  nails  is  always  in  excess  of  that  necessary  to 
)-each  the  clips  that  must  be  connected.  A  spare  pair  of  wires  is  left  project- 
ing at  the  end  of  the  cable,  so  that  it  may  be  used  in  case  any  one  of  the 


PACKERS  NEEDLt 


Fig.  6-30.— SWITCHBOARD,  TELEPHONE,   FORMING   CABLE  CONDUCTORS. 

regular  pairs  becomes  defective.  The  formed  part  of  Ihe  cable  is  sewed  u]) 
with  a  stout  waxed  linen  twine  liy  Ihe  aid  of  a  4-ineli  packer's  needle,  wliich 
facilitates  the  passing  of  the  twine  under  the  bunches  of  wire. 

This  needle,  with  the  method  of  tlirea<ling  it,  is  shown  in  figure  6-30.  Re- 
fore  sewing  up,  three  turns  of  twine  should  be  taken  next  to  the  butt,  drawn 
up  taut,  and  tied  with  the  knot  sliown,  in  which  •«  is  the  needle  end  of  the 
twine  and  b  the  short  end.  All  line  wires  are  bound  together  from  this  point 
to  the  end  of  the  twine  with  what  is  called  a  lock  stitch,  shown  in  figure  6-30. 

A  stitch  is  taken  at  each  nail,  and  if  the  space  between  is  over  1  inch  an 
extra  stitch  should  be  taken.  In  making  the  stitch  the  needle  is  passed  und(>r 
the  wires  and  througii  a  loop,  as  sliown  in  figure  6-31,  being  careful  not  to 
include  In  the  loop  tlie  stitched  part.  Tiie  loop  sliouid  liold  without  fastening 
after  being  completed.  The  last  stitch  is  reinforced  by  a  knot,  </,  after  which 
it  is  preferable  to  take  another  stitch  and  knot  h  around  the  spare  wires  and 
the  other  side  of  the  last  regular  pair. 

Before  taking  the  cable  from  the  forming  board  Ibe  ends  of  the  wires 
should  be  cut  off  even  and  the  Insulation  removed  from  the  ends  of  <>:ich, 
using  the  line  S  L,  figure  6-29,  as  a  gui<ie. 

(240) 


Post  Telephone  Systems. — Chapter  6. 


31 


The  skinnins  should  be  done  with  a  sliarp  knile,  drawing  it  from  the  line 
S  L  toward  tlie  end  of  the  wire,  at  the  same  time  pulling  olT  the  covering, 
which  will  slip  off  as  soon  as  the  threads  are  severed.  Great  care  must  be 
taken  not  to  nick  the  wire,  as  it  would  then  be  liable  to  break  at  this  point 
upon  being  moved  or  handled. 

The  tips  sh(juhl  now  be  shellacked  lightly  and  allowed  to  dry.  This  pre- 
vents unraveling  of  insulation  when  soldering. 

If  the  wires  are  to  be  soldered  to  the  terminal  clips,  their  bare  ends  should 
be  threaded,  through  the  holes  in  the  clips,  up  to  the  insulation  and  bent 
back.  If  no  holes  are  provided,  they  should  be  wound  close  around  the 
notched  portion  of  the  clip.  Care  must  be  taken  to  get  the  insulation  out 
of  the  notch  in  the  clip  or  the  hole.  Only  resin  solder  should  be  used  in 
making  soldered  joints.  After  soldering,  the  free  end  of  the  wire  should  be 
cut  off  close  to  the  clip  and  each  joint  tested. 

The  cable  should  now  be  strapped  in  place  with  leather  saddles.  When 
the  forms  are  installed  they  may  be  finished  with  a  coat  of  white  shellac, 
which  keeps  the  dust  and  dirt  from  sticking  to  the  wires  due  to  their  having 
been  boihMl  in  beeswax. 


Fig.   6-31.— SWITCHBOARD,    TELEPHONE,    FORMING   CABLE   CONDUCTORS. 

For  the  central  energy  board  of  from  50  to  100  line  capacity,  the  switch- 
board cables  are  sometimes  furnished  as  part  of  the  switchboard,  which  is 
usually  received  with  these  cables  connected  to  the  terminal  strips  on  the 
back  and  of  sufficient  length  to  reach  into  the  protector  cabinet  which  is 
erected  next  to  and  as  part  of  the  switchboard.  The  code  scheme  given  is 
followed  in  all  ^switchboard  wiring,  but  it  is  sometimes  impossible  to  make  up 
the  cable  for  the  protector  strip  on  a  temporary  form.  However,  this  is 
easily  met  as  follow^s: 

All  cables  are  butted,  as  previously  described,  at  the  bottom  of  the  arrester 
strip,  after  cables  are  measured  off  for  their  permanent  position.  The  wires  are 
then  boiled  in  beeswax,  as  instructed,  and  each  pair  brought  through  the  forming 
holes  of  the  protector  strip  in  the  same  order  as  their  connection  to  line 
signals.  That  is,  the  No.  1  signal  is  connected  to  the  No.  1  arrester,  then 
when  all  wires  are  in  place  the  cables  are  laced  into  one  stem  and  the  whole 
shellacked  and  soldered  as  in  the  first  case.  By  this  method  the  arrester 
strip  itself  is  used  as  the  form  for  lacing.  No  excess  slack  is  allowed  in  this 
form,  care  being  taken  to  connect  all  wires  correctly  the  first  time.  All  extra 
wires  are  run  to  the  top  of  the  form  and  dead-ended.  For  200-line  and 
larger,  central  energy  switchboards  which  have  iron  frames  for  supporting  their 
protectors  and  outside  line  cables  terminal  equipment,  and  which  are  erected 
separate  from  board  and  some  distance  from  it,  according  to  local  conditions, 

(241) 


32  Signal  Corps  Manual  No.  3. — Chapter  6. 

switchboard  cables  are  not  provided.  Tliese  must  l)e  made  up  locally  to  meet 
the  conditions. 

The  switchboard  will  be  supplied  with  one  or  more  spare  jacks  and  drojts. 
One  of  these  jacks  should  be  used  for  the  purpose  of  testing  cords.  The  magneto 
line  signal  shoidd  be  disconnected  from  the  spare  jack  and  a  cell  of  dry  battery 
should  be  connected  to  its  associated  line  terminals.  When  a  plug  is  inserted 
in  this  jack,  and  the  cord  is  shaken,  a  "  cut-out "  will  be  detected  by  a  rasping 
noise  in  the  operator's  receiver. 

The  generator  call  drops  should  be  adjusted  so  as  to  fall  readily  on  about  five 
cells  of  dry  battery. 

When  the  switchboard  is  completely  installed,  and  before  it  is  cut  over  to 
the  working  lines,  care  should  be  taken  to  test  for  cross  talk  and  incorrect  con- 
nections in  the  circuit  from  the  heat-coil  terminals  to  the  line  jacks.  Under 
no  conditions  should  the  switchboard  be  put  into  commission  when  any  cross 
talk  is  noticeable.  It  will  be  found  sometimes  that  the  key  contact  fails  to 
break  on  the  operator's  listening  circuit,  and  thus  crosses  the  lines  with  the 
other  keys.    Dampness  in  the  switchboard  may  also  cause  trouble  of  this  kind. 

All  power  connections  should  be  poled  alike. 

INSTALLATION    OF   PROTECTIVE   APPARATUS. 

It  is  the  practice  to  provide  protection  at  the  switchboard  room  for  all  lines 
entering  the  telephone  switchboard  even  though  not  any  of  the  line  circuits  are 
exposed  aerial  lines.  For  local  battery  systems  Mason  arresters,  or  similar 
individual  pair  arresters  consisting  of  a  fuse  and  a  multi-discharge  lightning 
arrester,  are  sufficient.  For  central-energy  systems  heat  coils  and  lightning 
arresters  are  provided. 

MAGNETO    SWITCHBOARD    PROTECTORS. 

The  protection  for  small  magneto  switchlioards  is  usually  installed  separately 
from  them ;  in  most  cases  on  the  wall  near  by  and  within  sight  of  the  operator. 
A  cabinet  of  the  same  wood  and  finish  as  the  switchboard  is  provided  for  the 
installation  of  the  necessary  number  of  Mason  arresters. 

The  connections  between  the  switchboard  and  the  protector  cabinet  should  be 
made  by  means  of  switchboard  cable  described  elsewhere  in  this  chapter.  The 
color  scheme  should  be  carefully  followed. 

The  forms  for  both  the  switchboard  and  protector  ends  should  be  carefully 
laced,  each  wire  being  brought  out  at  its  particular  line  spring  or  arrester. 
The  switchI)oard  end  should  be  carefully  soldered  after  the  wire  is  passed 
through  the  hole  and  wrapped  around  the  spring.  The  forms  srtould  be  treated 
in  a  similar  manner  to  that  described  for  common-battery  switchboards. 

If  the  switchboard  cable  is  installed  under  floor,  it  should  be  run  through 
bottom  of  switchboard,  coming  up  directly  under  the  point  of  arrester  cabinet 
it  is  desired  to  enter,  protecting  it  with  loricated  conduit  between  the  floor  and 
cabinet,  and  nnder  the  floor  provision  should  be  made  to  protect  the  cable  from 
moisture. 

The  outsid(>  lines  should  always  be  brought  into  the  oflice  and  cabinet  in 
cable,  even  though  the  length  of  calile  is  short.  If  over  12  pair  in  size  this 
cable  will  necessarily  be  pajter  insulation  with  lead  sheath,  and  .should  be  pot- 
headed  at  both  ends  to  terminate  the  conductors  in  rubber  insulation.  The 
method  of  pot  heading  is  described  in  chapter  4.  The  pot-head  sleeve  should 
extend  into  the  protector  cabinet  and  be  protected  by  loi'icated  c(>nduit  or 
frame  constrwction  between  the  floor  and  cabinet.  Inside  the  cabinet  the  pot- 
iK'ad  wires  should  be  carefully  laced  aflci-  the  wires  are  bi'ought  out  to  their 
respective  arresters. 

(242) 


Post  Telephone  Systems. — Chapter  6.  33 

These  forms  slioukl  l»e  thorouylily  sliollacked  after  tliey  are  formed,  laced, 
and  tied  in  place.  Never  i)our  liot  i»araftin  over  forms  of  pot-iioad  wire  as  tlie 
rubber  insulation  wuuli!  !•<■  injured  by  such  aetion. 

(KNTKAI,  K.\KK(iV  SWITCHBOARD  I'KOTECTOKS. 

One  pair  of  lijilitninj,'  iirresters  and  heat  coils,  as  shown  in  figures  6-8  and 
6-9,  are  provided  for  each  line,  both  central  energy  and  magneto.     In  addition 
a  strip  for  terminating  the  outside  cable  pairs  is  provided  which  usually  ex-  ■ 
ceeds  tlie  arrester  pairs  by  80  per  cent,  as  nece.ssarily  more  outside  <-ab!e  pairs 
are  installed  than  will  be  actually  used  by  lines. 

These  arrester  and  line  strips  for  the  50  and  100  line  .switchboards  are  in- 
stalled in  a  cabinet  such  as  is  shown  in  figure  6-32. 

The  cabinet  shown  is  erected  against  the  telephone  switchboard  and  bolted 
thereto  so  that  in  effect  they  comprise  one  cabinet  or  fixture.  The  local  con- 
ditions may  affect  their  relative  positions,  but  the  door  of  the  protector  cabinet 
can  be  hinged  on  either  side  and  the  strips  changed  inside  so  any  condition  can 
be  met. 

The  two  cabinets  are  exactly  alike  in  finish  and  essential  dimensions  and 
built  to  be  erected  together. 

The  switchboard  cables  from  the  50  and  100  line  switchboards  are  usually 
connected  to  that  end  when  received,  and  sufficient  length  allowed  for  connect- 
ing to  the  arrester  strip  in  the  protector  cabinet,  to  which  they  are  run  by 
cutting  a  hole  in  the  bottom  of  the  partitions  between  the  two  cabinets,  and 
lacing  the  cables  together. 

The  switchboard  cables  are  "  butted  "  and  formed  as  described  in  this  chapter, 
the  color  code  being  followed  carefully,  and  corresponding  numbers  on  the  arrester 
strip  assigned  to  line  signals  of  same  number.  The  magneto  drops  ai"e  con- 
nected innnediately  below  the  central  energy  lines,  allowing  for  full  capacity  of 
the  switchboard.  The  full  protector  equipment  iff  furnished  in  the  protector 
cabinet  for  each  central  energy  switchboard. 

The  20-pair  cables  are  boiled  in  beeswax  preferably,  or  paraffin  if  necessary, 
and  laced  up  into  one  form  and  strapped  securely  to  the  back  of  strip  on  whieh 
arresters  are  mounted,  as  shown  in  figure  6-32.  The  wires  should.be  carefully 
soldered  to  the  springs,  first  wrapping  the  wire  around  notch,  which  is  alreaily 
tinned.  '  ' 

Switchboard  cable  sometimes  supplied  by  manufacturers  with  switchboards  is 
insulated  with  two  silk  and  one  cotton  covering  and  has  no  particular  moisture- 
resisting  qualities.  It  should  never  be  installed  under  a  fioor  where  it  may 
become  wet  from  scrubbing  or  by  any  other  means.  It  will  retain  its  insulation 
when  installed  in  a  dry  room,  but  it  is  not  intended  for  exposure.  Neither 
should  this  type  of  cable  be  used  for  potheading  the  outside  line  cables. 

The  cables  to  the  outside  circuits  shou'd  lie  brought  to  the  cabinet  in  the  most 
workmanlike  manner  that  will  meet  the  local  conditions.  It  is  usually  possible 
to  bring  them  into  the  switchboard  room  directly  under  the  cabinet  by  running 
in  walls  and  under  floors.  Whenever  the  cables  are  exjio-sed  in  the  headquarters 
building  they  should  be  protected  by  loricated  coniluits  or  frame  runway.  In 
terminal  cabinets  they  should  be  potheaded  directly  inider  the  line  terminal 
strip  and  arranged  to  be  strapped  to  the  horizontal  angle-iron  piece  holding 
the  arrester  and  line  terminal  strips.  It  may  be  necessary  to  move  this  iron 
toward  the  front  of  the  cabinet  or  provide  a  new  iron  strap,  as  the  space  usually 
left  between  the  iron  strip  furnished  and  the  removable  rear  door  is  insufficient 
for  the  cable.  The  potheads  and  wiped  splices  shoulil  rest  directly  on  the  floor 
of  the  cabinet  and  thus  take  up  any  strain  that  may  be  on  the  cable. 

(243) 


34 


Signal  Corps  Manual  No.  3. — Chapter  6. 


Signal  Corps  pothead  wire  should  always  be  used  for  these  potheads,  and 
where  several  cables  are  brought  in  they  are  laced  into  one  form  on  the  back  of 
the  line-terminal  strip  to  which  they  are  connected. 

Rubber-insulated  wires  should  never  be  boiled  in  beeswax  or  paraffin,  but  the 
forms  should  be  shellacked  after  they  are  laced  and  soldered  in. 

The  potheads  should  be  carefully  aligned  when  installed  and  an  effort  made 
to  use  sleeves  of  the  same  length  and  diameter,  so  that  the  tops  will  be  level 
when  they  ai"e  completed. 


Fig.  6-32.— SWITCHBOARD,   TELEPHONE,    50-100   LINE    AND    PROTECTOR   CABINET. 


It  will  be  found  desirable  to  install  the  arrester  cabinet  on  the  right-hand 
side  of  switchboard,  facing  it,  as  this  will  bring  the  cros.s-connecting  springs 
for  intercoiuiecting  the  switcliboard  cables  terminating  on  the  light  iiiiig  arresters, 
and  therefore  the  outside  line  cables,  next  to  each  other,  simplifying  the  cross- 
corniection  work. 

This  will  n'(niii'e  that  liic  door  he  hinged  on  llic  rigiit  side.  An  illustration 
of  this  type  Is  .shown  in  figure  G-32. 

(244) 


Post  Telephone  Systems. — Chapter  6. 


:^5 


Outsido  liiip  cables  art'  lirou.ulit  to  tlu'  main  inm  I'raiiies  i»i-<tvi.l<-<l  U,r  liiMi-linc 
boards  in  tbc  saiiu'  maniUT  used  for  sinaHcr  s\\  itdibdards. 

At  tbc  main  framt-  tbe  caljies  arc  lir(»n;rbt  tlwoii^ii  tbc  lioor  in  a  positinri 
depending  on  tlic  20-pair  line  Itlocks  to  wiiicii  tlicy  arc  assiy;ticd. 

'I'lic  pol  beads  rest  on  tlie  floor  and  are  l)rou;,dit  ui»  lieside  tiie  vertical  line 
of  iron  braces  holding:  tbc  line  blocks  to  \vlii<-li  tin-  cables  are  connected.  The 
cables  to  be  connected  to  tbe  top  line  terminals  will  naturally  be  l)rou{,'lit  ia 
farthest  from  the  bottom  block.  The  potheads  should  preferal)ly  be  of  same 
size  and  height  of  sleeve  and  the  wires  carefully  laced  and  shellacked  when 
formed  and  in  place.  The  form  should  be  carried  straif^bt  up  and  branched  to 
the  blocks  at  the  iron  braces,  to  which  tliey  should  be  neatly  fastened  by  tajte. 

The  line  blocks  number  from  the  top  down,  and  spare  blocks  siiould  ordinarily 
be  left  at  the  bottom.  A  cable  should  be  distributed  on  on«'  vertical  row  of  line 
terminal  blocks. 

POWER   EQUlPifEXT   FOR    COMMON    HATTERY    POST    TELEPHONE    .SYSTEMS. 

The  necessary  current  for  the  operation  of  a  conmion  battery  or  central 
energy  telephone  .system  is  obtained  from  one  or  more  storage  batteries.  These 
batteries  and  all  necessary  apparatus  used  in  charging  them  should  be  given 
consideration  when  tbe  installation  of  a  common  battery  telephone  i^y.steni  is 
contemplated. 

The  power  equipment  is  one  of  the  most  important  features  of  the  common 
battery  telephone  system,  and  particular  care  must  be  exercisetl  in  its  installa- 
tion to  insure  reliability  of  service,  as  failure  of  the  battery  renders  the  entire 
system  inoperative. 

At  Coast  Artillery  posts  current  for  the  operation  of  post  telephone  system 
is  usually  obtained  from  storage  battery  installed  in  the  fire-control  switch- 
board room  in  connection  with  the  fire-control  system.  Tliese  batteries  are 
usually  of  either  80  or  1120  ampere  hour  capacity,  depending  upon  the  size  of  the 
fire-control  system. 

The  administration  building,  where  the  post  telephone  switchboard  is  located, 
may  be  a  considerable  distance  from  the  tire-control  switchboard  room,  and  the 
number  of  i)airs  in  a  cable  necessary  for  a  suitable  battery  feed  under  such 
conditions  would  be  determined  by  consulting  the  following  table : 


Number  of  circuits  in  use  simultaneously. 12345678 


10 


Number  of  pairs  required.  No.  1'.' 


Distance  from  battery: 

fyOO  feet 

l.OOOfeet 

l,.')00feet 

2.000feet 

2,o00  feet 

3,000feet 

3,.500feet 

4,0nOfeet 

1,500  feet 

5,000  feet 

5,500  feet 

6,000  feet 

(),500  feet 

7,000  feet 

7,500  feet 

8,000feet 

8,500  feet 

9,000  feet 

9,500  feet 

10,000  feet 


1 

, 

, 

1 

f 

1 

2 

2 

2 

•) 

1 

2 

2 

2 

2 

2 

L' 

2 

2 

2 

2 

o 

3 

2 

2 

2 

3 

3 

3 

2 

2 

2 

3 

3 

3 

2 

2 

3 

3 

4 

4 

2 

2 

3 

4 

4 

4 

2 

2 

3 

3 

4 

4 

5 

2 

2 

3 

4 

4 

5 

.S 

(1 

2 

2 

3 

4 

.5 

5 

6 

t") 

2 

» 

3 

4 

5 

6 

fi 

7 

2 

.3 

3 

4 

5 

6 

2 

.1 

5 

6 

6 

o 

3 

S 

6 

7 

T 

3 

5 

6 

7 

> 

y 

> 

4 

fi 

7 

/ 

K 

^9  1 

■ 

1 

- 

fl 

7 

n 

9 

10  1 

(245) 


36 


Signal  Corps  Manual  No.  3. — Chapter  6. 


With  this  arrangement  it  is  well  to  bridge  the  battery  feed  at  switchboard 
end  with  a  condenser  of  approximately  8  niicrofarids.  This  condenser  tends 
to  short  circuit  the  talking  currents  and  maintain  an  approximately  constant 
E.  M.  F.  at  the  switchboard  bus  bars.  Condensers  in  each  cord  circuit  bridged 
across  the  supervisory  signals  also  reduce  the  tendency  to  cross  talk. 

At  posts  where  existing  storage  battery  is  not  available  one  or  more  must 
be  supplied.  It  should  be  located  as  near  as  practicable  to  the  switchboard 
and,  although  not  desirable,  may  be  installed  in  the  same  room.  When  the 
latter  location  is  decided  upon  a  suitable  cabinet  should  be  constructed  for 
the  battery.  This  cabinet  should  be  painted  inside  (two  coats)  with  acid- 
proof  paint  and  equipped  with  one  or  more  vents  leading  to  the  outside  of  the 
building.     Figure  6-33  shows  such  an  installation. 


Fig.  6-33.— C.  B.  TELEPHONE  SYSTEM,  POWER  EQUIPMENT  IN  SWITCHBOARD  ROOM. 

Tlie  ideal  arrangement  for  the  larger  systems  is  to  have  :i  sei)atate  room, 
well  lighted  and  ventilated,  for  the  storage  battery  alone.  It  can  then  be 
mounted  on  appropriate  stands  where  they  Can  be  conveniently  examined. 
Next  to  this  room  should  be  the  power  switchboard  room,  where  is  located  the 
l)Ower  switchboard  used  in  controlling  the  power  circuits,  the  motor  generator 
used  for  charging  the  storage  battery,  and  the  dynamotor  or  other  apparatus 
for  furnishing  the  ringing  current.  An  additional  room,  well  lighted  and  ven- 
tilated, will  be  required,  in  wliich  is  located  the  telephone  switchboard  and 
distril)Uting  fi-ame  with  all  jtrotector  ai)paratus.  The  latter  room  should  be 
of  such  size  that  an  army  bunk  may  be  placed  therein  in  addition  to  the 
telephone  ai)paratus,  in  order  lliat  a  night  opi'rator  may  sleep  in  proximity 
t(i  the  switchboard. 

Ill  some  inslMtices  the  storage-battery  room  siiid  ]i(iW(>r-switchboard  room 
liave  been  foriiied  by  the  construd  ion  of  ;i  pnrtitioii  in  a  i-ooiii  in  the  basement 
of  the  a<Inniiistration  building,  thereby  iiinUiiig  two  suitable  rooms  of  one 
room.  Tlu!  telephone  switchboard  and  distributing  frame  should  not  be  located 
in  a  room  the  floor  of  which  is  below  tlie  ground  level.  Where  the  battery  re- 
(|Mlred  does  not  exceed  24-:iini)er('  hour  cajiacity  the  two-plate  or  coupled  type 
may  be  used,  thereby  niiniuiizing  the  amount  of  space  necessary. 

(246) 


Post  Telephone  Systems.^Ihapter  6. 


37 


In  the  past  it  has  l)eon  customary  to  furnisli  two  storage  batteries  in  order 
tliat  one  may  be  intermittently  disconnected  from  tiie  teleplione  switchboard 
while  being  charged  or  examined.  Experience  lias  shown  this  practice  to  be 
uneconomical  and  in  future,  where  the  battery  is  charged  by  a  generator,  the 
standard  equipuit'iit  will  be  one  battery  (ordinarily  12  cells).  If  the  tele- 
phone lines  are  noisy  during  the  charging  of  storage  battery,  a  suitable  dinke 
coil,  connected  in  series  with  one  of  the  leads  between  the  g('nerat(»r  and 
storage  battery,   will   usually  eliiiiiiiate  sudi   ;i   defect. 


Fig.  6-34— C.    B.   TELEPHONE   SYSTEM,    MOTOR   GENERATOR. 


Part 
No. 


Name. 


Rpferpiice 

No. 


Armature,  complete 

Armature,  dynamo 

Armature,  motor 

Box,  journal,  set  screws  for 

Boxes,  journal,  complete 

Brush  holder,  dynamo,  left 

Brush  holder,  dynamo,  right , 

Brush  holder,  motor,  left 

Bru.sh  holder,  motor,  right 

Brush  and  t erniiiial  stud 

Brush  and  terminal  stud,  nut  for , 

Brush  and  terminal  stud,  brass  washer  for. 

Brushes,  dynamo 

Brushes,  motor 

Bushing,  porcelain 

Coil,  field,  d^^^amo 

Coil,  field,  motor  (state  voltage) 

Connection,  drawing 

Coupling 

Feet,  rubber 

Generator  end,  complete 

>totor  end.  complete 

Name  plates 

Name-plate  screws 

Oil  cock,  J-inch -. 

Oil-well  plugs 

Pole  shoe 


Pole-shoe  screw ... 

Shield  cap,  screws  for. 

Shield,  connecting 

Shield,  front 


(247) 


38 


Signal  Corps  Manual  No.  3. — Chapter  6. 


With  small  Installations,  where  tlie  storage  battery  is  charged  from  a  direct 
current  lighting  main  through  lamps,  two  separate  storage  batteries  will 
invariably  be  installed,  for,  if  telephone  switchboard  is  connected  to  storage 
battery  being  charged,  the  electric  lighting  circuit  is  in  electrical  contact 
with  all  telephone  lines  radiating  from  telephone  switchboard,  a  condition 
which  should  never  be  permitted. 

Where  the  post  lighting  system  is  of  alternating  current  the  storage  l)at- 
tery  must  necessarily  be  charged  by  means  of  a  motor  generator  or  suitable 


°C/rcu/£ffrea/rer 


"(1 
/9eci/f/er  rude 

/?egu/a6/h(f  Compensator 


Bac/r  >'/<?>*' 
of  Pane/ 


^     V  Xf- 


66ar6/nff 
ffes/siance 


ffeac6ance 


Fig.  6-35.— C.  B.  TELEPHONE  SYSTEM,   MERCURY  ARC   RECTIFIER. 

(248) 


Post  Telephone  Systems. — Chapter  b. 


39 


(See  fig.  6-35.) 


Part 
No. 


Name. 


Panel,  control 

Panel,  control,  supporting  frame  for. 

Circuit  breaker,  C.  G.  type 

Ammeter 

Voltmeter 

Switch,  S.  P.  D.  T.,  combined  start- 
ing and  load 

Switch,  S.  P.  S.  T.  (au.xiliary),  for 
starting  anode  circuit 

Switch,  D.  P.  S.  T.,  for  A.  C.  line.. 

Switch,  ()-point  (controlled  by  hand- 
wheel) 


Refer- 
ence 
No. 


Part 
No. 


Name. 


Refer- 
ence 
No. 


Switch,  11-point  (controlled by  hand- 
wheel) I       10 

Fu.se  clip,  with  fuse,  S.  P.  D.  T 11 

Handwhecl  for  tube  holder '       12 

Tube  holder ;        13 

Tube,  rectifler |        14 

Resi.slante,  starling  load I        15 

Resistance,  starling  anode ' 

C'ompen.sator,  regulating i        Iti 

Reactance,  A.  (".  series 17 

Transformer,  insulating 


current  rectifier.  The  former  is  the  standard  method,  and  in  lisiinu  m.itHriiil 
tor  a  post  teleplioue  system  information  must  be  furnislied  concerninfr  the 
availal)le  current,  which  will  embody  the  following:  Voltage,  number  of  phase.^. 
and  number  of  cycles.  Figure  G-34  shows  the  construction  of  tlie  motor  gen- 
erator except  that  the  one  shown  is  equipped  with  a  direct-current  motor. 

Figure  (5-35 •  shows  the  mercury  arc  rectifier  which  has  been  furnislu'd  in 
special  cases. 

POWER    SWITCHBOAEDS. 

Signal  Corps  specification  No.  519  relates  to  teU*iiiione  imiuii  >\\  lu  iilmards. 
There  are  five  types,  in  order  that  all  varying  conditions  can  be  met.  Figure 
6-86  shows  the  type  No.  1.  and  figure  6-37  shows  the  type  No.  4.  Willi  type 
No.  1  the  batteries  are  charged  l)y  means  of  lamp  resistance,  and  with  the 
type  No.  4  a  motor  generator  is  used  for  charging  the  battery.  Tliese  panels 
are  intended  for  installation  about  18  inches  from  the  wall,  but  their  supporting 
frames  are  so  constructed  that  tliey  do  not  have  to  be  braced  to  wall,  conse- 
quently they  may  be  placed  any  distance  desired. 

It  may  be  necessary  to  install  between  the  post  electric-lighting  circuit  mains 
outside  of  administration  building  and  power  switchboard  two  additional  con- 
ductors, for  the  reason  that  the  electric-lighting  mains  to  the  building  may  be 
of  such  size  that  they  would  not  be  capable  of  carrying  the  excess  current 
necessary  for  charging  the  storage  batteries,  or  they  may  be  of  such  size  and 
length  that  the  excess  current  would  occasion  such  tlrop  in  voltage  that  the 
electric  lights  in  the  administration  building  would  be  dimmed.  Should  the 
installation  of  the  above-mentioned  leads  be  resorted  to,  it  is  desirable  to  enter 
the  building  by  means  of  duplex  power  cable  in  undergi'ound  conduit.  The 
cable  should  terminate  in  building  at  a  fuse  block  which  should  be  connecte<l 
with  a  knife  switch.  From  knife  switch  leads  should  be  connected  with  watt- 
hour  meter  before  terminating  at  power  switchboard. 

Where  alternating  current  power  circuits  are  contained  in  iron  conduits  care 
must  be  taken  to  install  both  wires  in  the  same  conduit  and  to  have  the  conduit 
grounded. 

The  watt-hour  meter,  knife  switch,  and  fuse  block  referred  to  above  will  he 
supplied  by  the  Signal  Corps  and.  together  with  material  for  their  in.stallation. 
should  appear  in  estimate  of  apparatus  necessary.  Tlie  fuse  block  and  knife 
switch  should  be  inclosed  in  a  metal  box  or.  as  a  substitute,  a  wmiden  box  linwl 
with  asbestos.  Electric  current  consumed  in  charging  Signal  Corps  storage 
l>atteries  installed  in  connection  with  post  telephone  systems  at  interior  i>osts 
is  chargeable  to  Signal  Corps  appropriaiions  if  obtained  from  a  commercial 
source. 


40 


Signal  Corps  Manual  No.  3. — Chapter  6. 


Figure  6-S3  illusti-ates  an  installation  of  the  central  office  apparatus  for  a 
small  system,  where  direct  current  is  available  and  where  one  room  only  can 
be  obtained. 

With  this  arrangement  the  leads  from  the  switchl)oards  and  the  post  power 
should  he  brought  up  from  the  floor  in  loricated  conduit  fastened  to  the  wall, 
even  with  the  bottom  of  the  panel ;  from  this  point  the  lead  sheath  is  removed 


1 


IT'*  -i 


Fig.  6-36.— C.  B.  TELEPHONE    SYSTEM,   POWER    SWITCHBOARD,  TYPE    NO.  1. 

(250) 


Post  Telephone  Systems. — Chapter  6. 


41 


Fig.  6-37.— C.   B.  TELEPHONE    SYSTEM.   POWER    SWITCHBOARD,  TYPE    NO.  4. 

46581°— 17 17  I -5 1.1 


42 


Signal  Corps  Manual  No.  3.— Chapter  6. 


and  the  wires  are  carried  over  to  the  connecting  lugs  on  the  rear  of  panel.  The 
exposed  parts  of  the  leads  should  be  painted  thoroughly  with  preservative 
paint.  If  the  storage  battery  cabinet  is  near  by,  the  leads  can  be  extended 
directly  to  it :  but  if  any  considerable  distance  separates  these  apparatus  their 
battery  leads  should  be  lead  down  to  the  floor  and  then  to  the  battery  cabinet 
in  the  same  manner  as  they  are  lead  to  the  panel.  As  previoiisly  stated,  lead- 
covered  cable  should  be  used  for  the  leads,  the  lead  sheath  being  cut  back  at 
the  end  for  connections.  Complete  instructions  for  installing  and  applying 
initial  charge  to  storage  batteries  appear  in  chapter  1  of  this  manual. 

RINGING    APPAKATIS. 

Ringing  apparatus  for  furnishing  ringing  current  for  calling  is  sometimes  fur- 
nished with  a  large  installation.  When  this  apparatus  is  used  it  is  only  neces- 
sary for  the  operator  at  switchboard  to  depress  proper  ringing  key  in  order  to 
call  party  desired,  thereby  obviating  the  manual  operation  of  the  switchboard 
generator.  The  change  from  dynamotor  to  switchboard  magneto  and  vice  versa 
is  quickly  accomplished  by  means  of  special  key  at  switchboard.  The  ringing 
dynamotor  has  been  furnished  by  the  Signal  Corps  in  most  instances. 

Telephone-power  equipment  is  sometimes  utilized  for  furnishing  primary  cur- 
rent for  the  dynamotor.  The  current  strength  required  for  these  sets  furnished 
to  date  is  approximately  2  amperes,  the  motor  feature  of  dynamotor  being  de- 
signed 'for  either  24-volt  or  30-volt  circuit.  An  80-volt  alternating  current  of 
approximately  I65  cycles  is  delivered  at  ringing  keys  of  telephone  switchboard 
by  the  dynamotor.    Figure  6-38  illustrates  this  apparatus. 


10  V.  A.C. 
/6 3  cycles 


To  telephone  switchboard 


Fig.  6-38.— C.  B.  TCLCPHONE  SYSTEM,   DYNAMOTOR,  RINGING, 
(252; 


Post  Telephone  Systems. — Chapter  6.  43 

The  iKlvniitage  in  having  dynaniotor  operate  from  these  voltages  instead  of 
the  post-power  voltage  is  that,  should  the  post  power  be  cut  olT,  the  dyuamotor 
can  be  operated  by  the  storage  battery  while  ordinarily  the  storage  battery 
charging  circuit  could  be  used  to  operate  the  dynaniotor.  The  latter  method 
is  usually  inefficient,  and  where  it  is  contemplated  to  furnish  a  dynaniotor, 
using  telephone-power  equipment  for  operating  it,  it  is  advisable  to  furnish 
storage  battery  of  such  capacity  that  the  dynaniotor  may  be  operated  thereby 
without  too  frequent  charging.  It  is  particularly  desirable  to  operate  the 
dynaniotor  by  means  of  telephone-power  equipment  at  places  where  power  plant 
supplying  post  power  is  not  operated  during  daylight,  a  condition  that  com- 
mercial telephone  companies  frequently  have  to  meet.  Under  such  conditions  an 
apparatus  termed  "  pole  changer,"  which  is  operated  by  primary  batteries,  is 
sometimes  supplied  for  furnishing  ringing  current. 

Where  there  is  a  relial)Ie  and  continuous  source  i)f  electric  power  it  may  be 
advisable  to  ojierate  the  dynaniotor  by  means  of  this  power.  If  power  be 
direct  current,  the  motor  feature  of  dynaniotor  must  be  designed  for  the  voltage 
of  the  circuit  available.  If  power  be  alternating  current,  a  motor  generator  is 
supplied.  Thus,  it  will  be  seen  that  conditions  should  be  carefully  surveyed 
before  deciding  upon  the  manner  of  furnishing  ringing  current. 

TELEPHONES. 

Telephones  used  in  connection  with  iiost-telephone  systems  are  of  the  com- 
mercial stanilard  type,  and  are  fully  described  in  chapter  3  of  this  manual. 

RECORDS   OF  AN    INSTALLATION. 

It  is  a  well-known  fact  that  in  no  branch  of  the  industrial  field  are  records  of 
such  great  importance  as  those  pertaining  to  electrical  installations.  While 
the  development  of  instruments  and  methods  employed  in  electrical  science  have 
reached  a  point  where  little  time  is  lost  in  locating  faults  and  in  repairing  or 
making  operative  an  electrical  circuit  that  becomes  inoperative,  accurate  records 
facilitate  to  a  marked  degree  such  repairs,  and  are  a  great  convenience  to  those 
vested  with  maintenance  of  the  systems. 

The  Signal  Corps  requires  that  upon  completion  of  installation  of  a  post- 
telephone  system,  a  comiilete  and  accurate  record  be  prepared.  This  record 
consists  of  standard  Signal  Corps  forms,  appropriately  accomplished,  and  draw- 
ings illustrating  routing  of  cables,  connections,  cross  connections,  and  special 
circuits  employed.  The  drawings  should  be  made  by  means  of  waterproof  ink 
on  tracing  cloth.  When  it  is  impracticable  to  make  the.se  drawings  at  post 
where  installation  is  made,  the  data  should  be  forwarded  by  person  in  respon- 
sible charge  of  the  installation  to  the  Departmental  Signal  Officer  of  department 
in  which  post  is  located.  The  Department  Signal  Officer  will  have  the  draw- 
ings made,  using  the  data  furnished  as  a  guide,  if  facilities  are  available  in  his 
office.  If  impracticable  to  make  the  drawings  in  the  office  of  the  Department 
Signal  Officer,  the  data  should  be  forwarded  to  the  Chief  Signal  Officer  of  the 
Army  with  request  that  the  drawings  be  made. 

When  drawings  have  been  approved,  complete  sets  (prints  of  tracings')  shall 
be  filed  as  follows :  One  in  office  of  Chief  Signal  Officer  of  the  Army ;  one  in 
office  of  Department  Signal  Officer,  and  one  or  more  at  office  of  post  signal  offi- 
cer. In  addition,  at  least  one  copy  of  drawing  .shown  under  subheading  "  a  " 
appearing  later  in  this  chapter  shall  be  transmitted  to  the  local  post  quarter- 
master, that  he  may  be  familiar  with  location  of  Signal  Corps  cable  and  conduit 
system.     If  there  are  facilities  for  changing  the  drawings   (tracings)   and  for 

(2p3) 


44 


Signal  Corps  Manual  No.  3. — Chapter  6. 


(■2-,4} 


Post   Telephone  Systems. — Chapter  6. 


/ 


./ 


c/ 


J8. 


.0-.9  ■'dOff/       ..       axl''^'""'^'''*nh„*«0 


avi^ 


5' 1 2 


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Ch,e  -Id-OS/  yp/r/s--»^ 

'j^bSS  -    -  -  -O-  -  A\<"^  ''J^,MM 


-a«-/         _« 


(255) 


46 


Signal  Corps  Manual  No.  3. — Chapter  6. 


making  prints  in  the  office  of  the  Department  Signal  Officer,  tlie  tracings  will 
be  filed  in  that  office,  otherwise  they  will  be  filed  in  the  office  of  the  Chief 
Signal  Officer  of  the  Army. 

The  iipkeep  of  these  records  is  of  utmost  importance.  All  authorized  changes, 
regardless  of  their  apparent  insignificance,  should  be  recorded.  It  is  the  duty  of 
post  signal  officers  to  see  that  all  modifications  of  the  original  system  are  re- 
ported to  the  Department  Signal  Officers.  Upon  receipt  of  satisfactory  data, 
showing  authorized  modifications  of  an  installation,  Department  Signal  Officers 
will  take  steps  to  have  the  drawings  (tracings)  corrected,  and  each  authorized 
office  furnished  with  corrected  copy,  at  the  same  time  advising  all  recipients 
that  the  forms  or  drawings  supersede  similar  ones  previously  furnished. 

Component  parts  of  the  record  are  enumerated  below,  and  the  items  as  de- 
scribed  should   be   strictly   adhered   to   in   order   that   post   signal   officers   ac- 


Str/P  */ 

-. 

/ 

3-/2 

2 

^-/o 

3 

4- 

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6 

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9 

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W 

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i 

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cn 

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fr> 

6 

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7 

8 

9 

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10 

/-2 

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12 

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33 
Cable 
3^ 


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2 

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3 

s-s 

4 

5 

6 

7 

8 

9 

10 

II 

12 

r5t/-/p 


#/ 


^U/p  *^ 


/ 

Off/cet-'i  Qtn 

2 

Cf-ft-s  Qtts 
B/dq  Si  a 

5 

4 

Off-i   Qtf-i 
a/at  J- 3  C 

5 

G 

7 

Offrs  QtrS 

8 

OfftS  Qr/-:> 

9 

10 

II 

IZ 

1 

%%%%V' 

a 

Lau/idf)/ 

3 

4- 

Off /-J  on  s 
a/etg  S2 

5 

6 

7 

8 

9 

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OttfJ  iftts 

// 

%%'f3'i>' 

12 

Srr/A  *  3 

/ 

Oitts  Oti-i 
B/aq  SI 

2 

OfffJ  Qtr-j 

5 

Offi-i  QtrJ 

4- 

OHti  Qtl-S 
3 fat  30 

S 

6 

7 

8 

9 

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// 

12 

Otfi--i  OtfS 

tSt/-/'p  *'^ 


/ 

%UFI^' 

z 

mf^' 

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l.au/ui/f 

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(o 

7 

8 

9 

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Fig.  6-41. 


-TELEPHONE  SYSTEM,  RECORD,  CONNECTIONS  AND  CROSS  CONNECTIONS 
OF  CABLE  CONDUCTORS. 


(266) 


Post  Telephone  Systems. — Chapter  6. 


47 


custonUMl    to   the   record    at   (Hie   pdsl    will    lie    fainiliur    as    far   as   iiracticalile 
with  tlie  records  at  anotlier. 

manhole:    No.  102. 

■Showtnc^  Location. 


1 

BARR/JCKS 
BLDG.  248.                     BLDG.249. 

fbunctation  >vcill. 

1 

V      ^H::          . 

H 


Manhole  cover  s'x  inches  below 
surface,  of  ground 


M.H.  No.  102 
Fig.  6-42.— TELEPHONE    SYSTEM,    RECORD.    LOCATION    OF    MANHOLES. 

(a)  Drawing,  map  to  scale,  showing'  routini,'  of  all  Signal  Corps  cables  and 
aerial  lines  and  the  location  of  all  substations,  torniinals,  and  all  principal 
structures.     (See  fig.  6-39.) 


Sfonaft  i^tUry  ffMn 


•Fbfnr  SA'hf  /S~*  f" 


7i4v^S»»    Sn«W  ami^  Rm» 


Fig.  6-43.~TELEPHONE  SYSTEM,    RECORD,    ARRANGEMENT    OF    POWER    EQUIPMENT. 


(257) 


4£ 


Signal  Corps  Manual  No.  3.— Chapter  6. 


1 


y^-R»sB/lR 


-ipo  PkrkaC 


=^^ 


i  /.//',! 


Cosfl  5 )"l'\'*'^t>  *>*"■• 


5oo'^J)ftoP 


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■6'p/:cifli.   Ud/niivc,   Di?op**JS   rln  Ncn/  London  T/ii/Nn. 
FoaT  Ha   U/f?iav>T.   NlY. 


TS'ei/t  Bnn.  Utf  ofOnop  PHfEt.- 


ToFiiftMi'.cr  Do  It  no 


CO  si\. 


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pop  or   SlQ.Nei,\ 


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53 


No  or 


7i-rrr>inal  Beard. 

Fig.  6-44.— TELEPHONE    SYSTEM,    RECORD,    SPECIAL  CIRCUITS. 


(2G8I 


Post  "1  elephone  Systems. — Chapter  6. 


49 


(h)  Drawing,  diagram,  not  nece.ssaril.v  to  .scale,  for  each  post,  showing  the 
distances  between  all  manholes  and  the  distance  between  terminal  manholes 
and  end  of  each  cable  terminating  in  adjacent  stretch.  This  diagram  should 
show  slack  of  each  cable  in  each  manhole,  as  well  as  location  of  .si»Iiees  in 
each  cable.  In  indicating  slack  it  may  be  necessary  at  times  to  have  such 
indication  a  minus  quantity  ;  this  is  due  to  the  fact  that  the  amounts  entered 
should  be  tlu'  difference  between  a  straight  line  through  manhole  and  actual 
path  taken  by  cable  in  the  manhole.  Diagram  should  also  show  in  tabidated 
form  the  number,  the  type,  and  the  total  length  of  each  cMble.      (See  liu'.  0-40.) 


1 

> 

6 

O 

V 

Q 
0 

6 
o 

0 

c    +-• 

+- 
c 

E 

t; 

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o 

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Guard  Avo  us^ 

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1) 

IX 

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Or  f^oi  fer  Of -p. 

C  B   Wall 

3lf, 

li. 

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Corr,m,S3^KY 

31*1 

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it34 

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n 

It 

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C  B       ■■ 

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A^ty  f"?'.  Offi 

C.  B  IA*>//  . 

JJtJI 

Fig.  6-45.— TELEPHONE    SYSTEM,    RECORD,    CONNECTIONS,    AND   OTHER    DATA. 

If  the  data  enumerated  under  this  heading  can  be  shown  on  map  referred 
to  under  heading  "  a  "'  without  crowding  the  entries  it  may  be  done,  thereby 
eliminating  additional  tracing. 

(c)  Di-awing,  not  necessarily  to  scale,  of  each  terminal  box.  submarine 
terminal  box,  junction  box,  distributing  frame,  and  arrester  cabinet  showing 
the  location  of  conductors  of  all  cables  terminating  at  that  pt»int,  all  cross 
connections,  the  use  of  each  circuit,  and  all  spare  conductors.     (See  fig.  6-41.) 

(d)  Drawing,  showing  exact  location  of  each  manhole  if  they  be  of  the 
type  having  cover  below  surface.  Measurements  shown  should  be  between 
permanent  substantial  construction,  such  as  nui.sonary  foundations  of  structures, 
if  possible,  and  njanholes.  (See  fig.  6-42.)  If  desire*!  a  number  of  these  may 
be  made  on  one  sheet. 

((■)  Drawing,  not  necessarily  to  .scale,  showing  arrangement  of  i>ower  tiiuii*- 
nieut.     This   is   not   necessary   with   local   l)attery   .sy.stems    (see   tig.  G-43i.     A 


(269) 


50 


Signal  Corps  Manual  No.  3. — Chapter  6. 


Sijinal  Corps  drawing  of  power  switchlioard  may  he  adcU'il  ti>  sliow  cirtniits  if 
it  is  applicable. 

(/)  Drawing,  not  necessarily  to  scale,  showing  eacli  special  cin-uit  if  there 
be  any  not  shown  in  this  manual.      (See  fig.  6-44.) 

(g)  Drawing,  diagram  showing  post-telephone  connections  and  other  im- 
portant data.      (See  fig.  6-45.) 

ADMINISTRATION     BUILDING 


orricE  OF  COMDG.  orriccp 


Normol  po5ihon  55  shewn*      ^ 


"5> 


ToSriBd-Sam    Nal 


M 


orrjCE   or 

StRGT  MAJOR 


To5w.BclSKjr. 


oo 


Fig.  6-46.— TELEPHONE    SYSTEM,    RECORD,    SPECIAL    ARRANGEMENT. 

(70  Miscellaneous  drawings  and  diagrams.  Under  this  heading  should  be 
included  drawings  or  diagrams  illustrating  any  part  of  the  installation  not 
covered  by  the  above  and  which  the  engineer  in  responsible  charge  of  installa- 
tion believes  should  be  elucidated.     (See  fig.  (3-46.) 

SIGNAL    CORPS    FORMS. 

(/.)  Form  No.  261  (cable  record)  should  be  accomplished  in  triplicate  for 
each  cable  of  the  system. 

(7)  Form  No.  211  (report  of  inspection  of  Signal  Corps  equipment )  should 
be  accomplished  in  triplicate.  As  the  name  implies,  Form  No.  211  is  a  form 
used  in  recording  results  of  inspection.  Inasnuich  as  this  form  requires  a 
great  amount  of  information  that  can  be  nuich  m(n*e  readily  secured  at  time 
of  installation  of  apparatus,  it  has  been  made  a  part  of  the  .standard  record. 

(k)  Form  No.  209  (semiannual  i-eport  of  post  telephone  e(ini])ment)  slnmld 
be  accompli.shed  in  triplicate.  This  form  also  requires  information  that  sliould 
be  supplied  upon  completion  of  an  installation. 

(/)  Form  No.  279  (.summary  of  cost  of  an  installation)  sIkhiUI  be  accom- 
plislied  in  duplicate,  one  coi)y  foi-  ollice  of  Cluef  Sigiuil  Otlicer  of  the  Army 
and  one  for  office  of  Department  Signal  Officer. 

ivi)  Form  No.  204  (report  on  the  progress  of  iiistallalioiis).  During  the 
l>rf)gress  of  installation  of  a  post  teI(>i>hoiie  system,  where  the  work  involved 
re<iuires  more  than  one  month  t<»  complele.  (liis  form,  accomi»lished  in  dupli- 
cate, will  be  forwarded  by  person  in  i-espunsilile  cliarge  of  woi-k  lo  tlie  De- 
partment Signal  Officer.  Th(>s(>  foniis  will  be  I'oi-warded  at  the  end  of  each 
calendar  nionlii,  an<l  iiiion  comiilcl  ion  of  ilie  work  if  such  (■((niplflioii  does  not 
occur  on  last  <!ay  of  calendar  monlli.  <  »nc  of  lliese  forms  will  be  filed  in 
office  of  Chief  Signal  Officer  of  the  Army  and  one  in  office  of  the  Department 
Signal  Officer. 


(260) 


Post  Telephone  Systems. — Chapter  6.  51 

(n)  Form  No.  210  (montlily  report  of  einiiloyees  at  large).  The  person  in 
responsible  charge  of  installation  will  collect  at  the  end  <»f  each  calentlar 
month  a  single  copy  of  this  form,  duly  acconii)lishe(l,  from  each  electrical  en- 
gineer, assistant  electrical  engineer,  and  electrical  assistant  engaged  on  the 
work,  and  will  forward  these. forms,  together  with  one  copy  of  the  same  form 
accomplished  by  himself,  if  he  be  a  civilian  employee  of  the  Signal  Corps, 
to  the  Department  Signal  Officer  of  the  department  in  which  he  is  operating. 
This  form  is  for  the  hies  of  the  office  of  the  Chief  Signal  Ollicer  of  llw  Army. 

Maintk.nanck  ok  I'o.st  Tki.ki'honk  Systems. 

summary  of  faltlts  th.vr  akk   .most  i.lkkl.y  to  occik  a.ni)  an   knr.mkkatlon 

of  causks. 

loc.\l  battery  ix.strl.ments. 

(«)  L.  B.  station  can  not  riiui  another  station. — Defective  apparatus  at  other 
station.  Broken  wire  in  either  instrument.  The  coiled  spring  on  magneto 
driving  shaft  broken.  Open  circuit  in  magneto  windings.  Contact  piece  at 
end  of  magneto  armature  shaft  bent  or  broken.  Open,  crossed,  or  grounded 
lines  external  to  instrument.  If  any  of  the  latter  faults  exist,  unless  line 
is  short  circuited  the  home  station  should  be  able  to  ring  its  own  ringer. 

(6)  L.  B.  station  dors  not  receive  a  ring  from  another  station. — Distant  in- 
strument defective.  Home  station  ringer  out  of  adjustment  or  permanent 
magnet  weak.  Open  circuit  in  ringer  magnets  or  broken  wire  in  ringer  cir- 
cuit. Failure  to  operate  of  magneto  automatic  cutout.  Elxternal  line  open 
or  short  circuited. 

(c)  L.  B.  station  can  not  transmit  speech  to  distant  station. — Distant  sta- 
tion apparatus  defective.  Hook  switch  contacts  out  of  adjustment.  Local 
battery  weak  or  open  circuit  in  primary  circuit,  including  winding  of  induc- 
tion coil.  Open  circuit  in  secondary  winding  of  induction  coil,  receiver,  re- 
ceiver cord,  or  instrument  wire.  Packed  or  defective  transmitter.  External 
line  open  or  short  circuited. 

(d)  L.  B.  station  can  not  receive  speech  from  distant  station. — Distant  .sta- 
tion apparatus  defective.  Hook  switch  contacts  out  of  adjustment  or  broken. 
Defective  receiver,  such  as  open  circuit  in  cord,  windings,  or  diaphragm  dis- 
torted. Open  circuit  in  secondary  winding  of  induction  coil  or  instrument  wire. 
External  line  open  or  short  circuited. 

COMMON    BATTERY    IXS  I'RrXIENT.S. 

(n)  C.  B.  station  can  not  sifinal  siritchhoard  operator. — Defective  central 
station  apparatus.  Common  battery  cut  off.  Hook  switch  contacts  out  of 
adjustment  or  broken.  Open  circuit  in  primary  winding  of  induction  coil, 
transmitter  circuit,  or  instrument  wiring  of  these  circuits.  Open  or  short 
circuit  in  external  line. 

(6)  C.  B.  station  holds  operator's  signal  when  honk  is  down. — Short  circuitetl 
condenser.  Hook  switch  contacts  out  of  adjustment.  External  line  short 
circuited. 

(c)  C.  B.  station  does  not  receive  a  ring. — Defective  central  station  apiia- 
ratus.  Home  station  ringer  out  or  adjustment  or  permanent  magnet  weak. 
Open  circuit  in  condenser.  Open  circuit  in  ringer  nuignets,  or  broken  wire  in 
ringer  circuit.     External  line  open  or  short  circuited. 


(261) 


52  Signal  Corps  Manual  No.  3. — Chapter  6. 

id)  C.  B.  station  can  not  transmit  speech. — Defective  central  station  appa- 
ratus. Common  battery  cut  off.  Hook  switch  contacts  out  of  adjustment  or 
hrolven.  Open  circuit  in  primary  windin.ij  of  induction  coil,  transmitter  circuit, 
or  instrument  wiring  of  these  circuits.  Packed  or  defective  tran.smitter.  Ex- 
ternal line  open  or  short  circuited. 

(c)  C.  B.  station  can  not  receive  speech  from  distant  station. — Distant  sta- 
tion apparatus  defective.  Hook  switch  contacts  out  of  adjustment  or  broken. 
Defective  receiver,  such  as  open  circuit  in  cord,  windings,  or  diaphragm  dis- 
torted. Open  circuit  in  secondary  of  primary  winding  of  induction  coil  or 
instrument  wire.  Open  circuit  in  ti'ansmitter  or  transmitter  cord.  External 
line  open  or  short  circuited. 

(/)  Speech  at  distant  station  is  indistinct,  scratch iiifi  or  firating  noise  in 
receirers.—ljOOHe  connections  or  battery  too  strong.  (This  may  be  noted  dur- 
ing charging  of  telephone  storage  battery.)     Damaged  or  broken  receiver  cord. 

Note. — In  common  battery  transmission,  if  the  line  resistance  is  excessive  transmis- 
sion is  weakened.  Six  miles  of  cable  with  conductors  36  mils  diameter  is  considered  the 
limit  of  common  battery  supply  for  efficient   conversnt  ion. 

Telephone  Switchhoaru  Trovbles. 

summary  of  faults  which  are  most  common. 

(a)  Common  batter}/  siritchhoard,  visual  signal  is  feeble. — This  indicates  a 
poor  adjustment  in  the  signal  armature,  low  battery,  or  high  line  resistance. 

(b)  Common  battery  sioitchboard,  signal  is  irregular. — This  indicates  loose 
connection  either  in  the  switchboard,  switchboard  cabinet,  or  in  the  external 
circuit.     May  be  due  to  defective  jack  contacts. 

(c)  Common  battery  switchboard,  signal  icill  not  operate. — Weak  battery. 
Broken  wire  in  either  internal  or  external  circuit.  Signal  short  circuited  or 
signal  badly  out  of  adjustment. 

id)  A  grating  noise  noticed  n-hen  plug  of  connecting  cord  is  in.<ierted  in 
jack. — Voltage  of  battery  too  high  or  partial  open  circuit  in  the  connecting 
cord. 

(e)  Cross  talk. — If  the  .system  is  free  from  cross  talk  when  installed  and 
trouble  does  not  exi.st  in  the  exterior  sy.stem,  cross  talk  that  may  develop  is 
l)robabIy  due  to  the  sticking  of  the  listening-key  contacts  in  switchboard,  thus 
liridging  two  or  more  lines  together.  ^Moisture  in  terminal  boxes  or  moist  wire 
foi'ms  is  another  condition  which  sometimes  causes  cross  talk. 

(/)  In  lamp  line  switchboards  or  in  visual  signal  switchboards  equippeil  with 
lamp  supervisory  signals  the  tirst  step  shoidd  be  to  examine  the  relays  in  the 
event  of  switchboard  signal  trouble. 

With  any  switcliboard  where  it  is  determined  that  a  fault  exists  in  the  central 
station  the  proper  procedure  is  to  first  examine  tlie  lieat  coils  pertaining  to  the 
line  in  troui)le.  Having  determined  that  the  trouble  exists  within  the  switch- 
board, it  is  a  simple  matter  to  localize  the  fault  if  a  person  is  thoroughly 
familiar  with  the  circuits  <tf  th(»  .switchboard. 

If  the  repair  of  a  defective  switchltoard  circuit  is  urgent,  it  may  be  advisable 
t()  transfer  the  incoming  line  t<»  a  signal  not  in  use,  advising  the  switchboard 
operator  of  such  actif»n  and  reiiairing  the  de^fective  circuit  as  soon  as  i»racticaiile 
thereafter. 

In  cord  switi-hltoards  if  the  drop  does  not  fall,  test  first  for  continuity  of 
circuit  and  then  see  if  the  pivots  -.wi'  loose.  If  the  pivots  are  loo.se  the  arma- 
ture will  frecpiently  stick  and  fail  to  release  the  shutter. 

( 202 1 


Post  Telephone  Systems. — Chapter  6.  5'i 

Tf  wlicii  ;i  riiiir  coiiics  in  iikhc  IIimii  oiio  (lrii|i  lulls  il  niiiy  lie  i!iii>  to  ii  iniss 
ill  llic  lines  just  outside  of  tlif  iioaid.  or  else  on  ihc  li;rlitniiij:  sliij)  to  uliidi 
tlicse  lines  ;ire  connected.  Tins  can  he  readily  cleared  liy  ins]»ection.  The 
iroul)!*'  may  I»e  due  to  tiie  fact  lliat  tlie  contacts  on  the  magneto  side  of  some 
one  of  the  riuf^in;;  keys  are  not  broken  when  tlie  key  is  in  a  normal  position. 

WIu'ii  il  is  discovered  tliat  a  pair  of  conis  <lo  not  jierform  liieir  j)roiier 
f  uuctioii  they  sliould  be  tested  lor  au  opeu  or  for  a  "  cut-out." 

A  frequent  cause  of  trouble  in  the  jacks  is  due  to  the  fact  tliat  persons 
will  stick  pens  or  pins  in  them  and  break  off  the  points,  short-circuit  in?  tlie 
sju-inirs.  Tiie  only  way  to  (li.scover  this  is  by  thorough  inspection  of  the  jacks. 
To  see  whetlier  the  contacts  in  the  riniiiiifr  and  listeniuf:  keys  break  in  the 
liroper  manner  the  part  of  the  board  containing;  them  should  be  placed  between 
tlie  lijrlit  and  the  eye  of  the  inspector.  By  looking  at  tlie  keys  against  the 
light  and  opening  and  closing  them  it  will  be  discovered  whether  the  contacts 
break  properly  or  not.  Trouble  may  frequently  be  removed  from  the  cord 
circuit  l)y  cleaning  the  ti]i  and  sleeve  of  the  pbig  with  crocus  doth.  When 
a  switchboard  is  new  and  tirst  placeil  in  service  particles  of  metal  are  fre- 
(pieutly  found  in  the  jacks,  and  the  board  can  be  cleaned  by  using  a  lian<l 
bellows  and  blowing  (mt  all  of  the  jacks  thcu'oughly. 

The  accepted  method  of  cleaning  key  contacts  or  mechanically  testing  for 
opens  is  by  putting  a  strip  of  hard-surfaced  pafter  between  contacts  when 
keys  are  open,  closing  the  keys,  and  withdrawing  it.  If  the  key  does  not 
make  a  firm  contact  the  paper  will  be  easily  withdrawn,  and  this  trouble 
can  be  eliminated  by  adjusting  the  key.  If  it  does  make  a  firm  contact, 
withdrawing  the  paper  will  clean  off  any  dirt  that  may  be  on  the  contact. 

Drops  may  be  tested  by  using  the  short-circuiting  key  in  the  center  of  the 
lower  panel  of  the  telephone  switchboard  in  connection  with  the  test  jack. 
Plug  the  defective  drop  into  the  test  jack  and  press  the  button.  If  the  drop 
oiierates  freely  it  should  be  considered  satisfactory. 


(26a 


ClIAPTKH    7. 
SMALL-ARMS   TARGET   RANGE   SIGNALING   SYSTEMS. 

Piiriifi^rMiiIi  -(')-  (if  ••  Small-Anns  Firing  Maminl.   191.'^."  reads  as  follows: 

ChiHfirii. — Tli(M-e  are  two  classes  of  ranges :  Class  A  ranges,  which  are  more 
or  less  limited  in  extent  and  which  are  etiuipped  for  known  distance  practice; 
class  B  ranges,  which  are  of  extended  area  and  diversified  terrain,  and 
which  are  used  for  combat  tiring. 

The  Signal  Corps  furnishes  and  installs  material  and  apparatus  for  conunn- 
nication  for  class  A  ranges  referred  to  above.  Inasmuch  as  the  class  B  ranges 
are  often  temporary  in  both  arrangement  and  location,  no  fixed  signaling 
system  for  them  can  be  devised.  The  Signal  Corps  has  furnished  apparatus 
and  material  for  establishing  comnmnication  for  such  ranges,  the  installation 
being  made  by  detachment  of  troops. 

Class  A  ranges  only  are  considered  in  the  following: 

The  system  of  communications  to  be  furnished  target  ranges  depends  on  the 
type  of  range,  its  size  and  importance,  and  upon  local  conditions,  which  vary 
for  each  case.  Among  such  local  conditions  may  be  mentioned  the  character  of 
the  soil  and  the  necessity  for  using  the  i-ange  for  other  purposes,  such  as 
drill,  etc. 

In  general  the  systems  for  class  A  r;inges  may  be  divided  into  three  types,  as 
follows : 

Ti/itc  I. — This  system  is  ajiplicable  to  all  tyjies  of  ranges  and  provides  for 
telephonic  communication  only.  The  circuits  of  this  system  comprise  a  telephone 
line  from  extreme  end  to  end  of  the  range  with  outlets  at  each  firing  line  to 
which  a  portable  telephone  may  be  connected  by  means  of  a  flexible  cord  and 
plug.  The  line  is  preferably  laid  underground  in  trench  or  conduit,  lead- 
covered  or  lead-covered  and  armored,  rubber-insulation,  single-pair  cable  being 
used  for  this  purpose.  The  telephone  used  is  the  standard  camp  telephone  or 
ob.solete  field  telei)hone  fitted  with  cord  and  plug  for  attachment  to  outlet. 
Where  necessary,  the  telephone  may  be  placed  in  a  portable  shelter  box. 

This  type  of  system  is  used  on  small  or  unimportant  ranges  where  the 
expense  of  a  more  extensive  system  is  not  .iustitied,  or  for  provisional  work 
where,  on  account  of  lack  of  funds  or  other  causes,  it  is  not  possible  to  supply 
a  moi'e  complete  system. 

Tjiix:  ,i. — This  .system  of  communicalioM  is  applicable  to  targets  in  echelon 
only.     It  comprises  the  following  connnunications: 

{(i)  A  telephone  for  every  group  of  10  tiring  points  or  less  on  line  to  telejihone 
at  butts. 

(h)  A  push  button  at  each  tiring  point  connected  to  the  buzzer  at  the  corre- 
sponding target. 

(c)  An  ainunuiator  at  the  butts  of  2(T<)-yard.  .S(X)-yard.  ami  .'^(KVyard  ranges, 
with  a  drop  for  each  target  of  the  respective  ranges.  Each  drop  may  be  actu- 
ated by  associated  strap  key  in  rear  of  respective  target. 

(d)  A  master  switch  at  each  annunciator,  by  which  all  target  buzzers  may  be 
operated  simultaneously. 

r2Gol  I 


2  Signal  Corps  Manual  No.  3. — Chapter  7. 

Tliis  system  will  he  iuslalkMl  lUKk'rjiniuiid  in  trcncli  nr  coiuluit,  \isiii<,'  iiainT 
insulation  cable  for  longitudinal  runs,  and  rubber-insulation,  lead-coveretl.  and 
armored  cable  (t.vpe  2."il)   for  the  branches  at  the  tirinu  lines. 

'I'lljic  'i. — This  s.vstem  is  for  installation  at  target  ranges  having  only  onegrouj> 
of  targets,  the  sevenil  ranges  being  obtained  by  iilacing  the  tiring  points  behiml 
each  othiii".  The  equipment  corresponds  closely  to  the  type  2,  with  such  inoditi- 
cations  as  ai*e  necessary  to  adapt  it  to  such  arrangement.  It  provides  the 
following  c(innnunication : 

(o)  A  telephone  for  every  group  of  10  firing  points  or  less  on  line  to  telephone 
at  butts. 

(h)  Push  buttons  at  each  tiring  point  connected  to  a  buzzer  at  the  corre- 
sponding target. 

{(■)  An  annunciator  with  a  dro])  for  each  target,  which  (lro|)  may  be  actuated 
by  a  strap  key  at  associated  target. 

(il)  A  master  switch  at  the  annunciator  by  which  all  target  buzzers  may  be 
oiierated  sinndlaiu'ously. 


I  rc.'O'      PcrnU-Ze  <.or<J^ 


COVER . 

K.p    Leatlicr-^    Id    f;4"tli.ck 
Dar»*  Maroon  colu-' 
Close  fil  oil  base 


PLAN-ASSEMBLED-COVER  REMOVED 


CENTRAL -SECTION -ASSEMBLED 


Grass  pms    Tf€\ 


BASE  OF  PUSH   BUTTON     "4"    -.\oC~-jt>  7^ip  "^  rt"-; 

Red  F.ter  LINING    FOR 

THIMBLE 
Red  Fiber  .Oi5Th,i.k 


m 


£nd  re<:/uccd  inthfc^misi.^'^  ~ 


'-frrp- 


■2" -■^^     rtir. 


'^     U:      H 


^i 


-'--^i>-m  %\<^  <?  -  -I- 


'•^e^ 


EfH:/  rf^(/ure<//n  ff/trA/fcsa 


—    '-1^  1        I-     ;f  -  -  A 


Ned    FiUr    0.)..    Ilii(  k 


Fig.  7- 


CONTACT    SPRINGS 

Uo  20(  035')  Phosphor  Brou/c 


-S.    A.  TARGET    RANGE    PUSH     BUTTON. 


This  system  will  be  inslalled  unih-rgronnd.  using  itaper  insulation  cable  for 
runs  re(|uiring  a  large  nnmln'r  of  conductors,  and  type  12r»l  cable  for  distribution, 
the  same  as  for  the  type  2  system. 

It  will  be  noted  that  with  the  type  2  sysleni  the  200-yard.  .''.00-yard,  and  .500- 
,vard  ranges  are  supplied  with  aniiuncialor,  maslei'  switch,  and  strai)  ke.vs  in 
iiddilion  (o  llic  oilier  apparatus,  .hkI  thai  I  he  C.oo-yard.  SOO-yard.  and  1.000-yard 
I'angcs  arc  iiul  supplied  with  that  .-ipparat  us,  although  a  buzzer  is  inslalled  in 
rear  of  ea<-h  target,  making  the  Latter  a  buzzer  system  while  the  former  is  a 
buzzer  amnincialor  .system. 

(260) 


Small-Arms  Target  Range  Signaling  Systems. — Chapter  7.  3 

The  reason  for  this  is  that  the  annunciator,  master  switch,  and  strap  key  is 
apparatus  used  in  connection  with  raising;  and  h>\verinf;  tlie  targets  promptly 
and  simultaneously,  an  operation  pertaining  to  rapid-tire  practice.  Hapid-tire 
practice  is  lield  only  on  ranges  up  to  and  including  ."j(M)  yards. 

The  source  of  i)o\ver  for  operating  the  huzzer  system  and  also  the  liuzzcr 
amniMciator  system  is  20  cells  of  No.  0  reserve  type  dry  cells  of  hattery  (fcir 
di'scription  of  cell  see  diap.  1)  installed  in  distrihuting  box  upon' two  shelves 
provided  f«ir  thai  purpnse.  The  distrihiiiing  hox  is  descrilied  hiler  in  this 
chapter. 


Jtt  K  H  Bmii 


,  Pmis  plate  4''i^£, 


COf^kxTtSprinq  '203t^^i^ 


This  plug  some  as  mOC 
^  Cos  Marine  Ouflet    Mfrs 
Cat  fig  ZZ323 


iStandard  if' P'P*  tfireod 

\/4-  pr  in 


Fig.  7-2.— S.  A.  TARGET  RANGE  OUTLET  BOX,  ROUND  PATTERN. 

Each  group  of  targets  on  the  larger  ranges  is  usually  tniuipped  with  a  small 
structure  in  rear  and  in  proxinuty  to  parapet  wall.  This  structure  is  used  f<»r 
storing  targets  and  supplies  and  may  he  used  fur  range  olhcer's  station  during 
firing.  At  ranges  where  buzzer  annunciator  systems  are  installed  the  annun- 
ciator distributing  box  and  master  switch  should  he  locatinl  in  this  structure  if 
practicable.  In  some  instances  the  Signal  Corps  has  constructetl  a  small  frame 
booth  in  the  form  of  a  lean-to  again.^t  parapet  wall  for  housing  this  api)aratus. 
The  booth  was  equipped  with  a  slide  window  on  eitlier  side  in  order  that  range 


46581°— 17- 


-IS 


(267) 


4  Signal  Corps  Manual  No.  3.— Chapter  7. 

officer  might  observe  the  actions  of  men  at  targets.  It  was  also  equippeil  with  a 
tight  roof  and  door  with  substantial  lock  in  order  that  when  range  was  not  in 
use  contents  of  booth  might  be  made  secure. 


PLU«  CONTACTS. 


Fig.  7-3.— S.    A.   TARGET    RANGE    OUTLET    BOX,    1915    MODEL. 

The  target  range  outlet  boxes  for  the  push-button  attaclnueuts  should  be 
located  approximately  10  feet  in  rear  of  each  firing  point,  as  scorers  are  required 
to  be  seated  close  to  and  in  rear  of  the  firing-point  stakes. 

The  push-button  attachments  should  be  removed  and  stored  in  a  dry  room 
upon  completion  of  each  day's  practice  during  inclement  weather  and  wlien 
target  practice  is  suspended  for  a  period  of  days. 


1  I  pair  lead  centred  cobir 


't 1.. 


->J 


Ityrf/p/i  t/7tle 


\E\_     ^^_ 


CuUrl  «o-«J 


=gl 


ysr. 


^ 


Pig.  7_4._S.    A.   TARGET    RANGE,  TYPE    NO.    1     SYSTEMS. 


(268) 


Small-Arms  Target  Range  Signaling  Systems. — Chapter  7.  5 

The  pusli-hintoii  ;in;ichun'iil  cniisisls  nf  ii  i\\  n-(<iii(lii<tiii-  llcxiliU'  ciifd.  Mpproxi- 
niately  0  tit>t  in  len^rtli.  eiiuipped  iit  one  cml  wiili  a  si>eri:illy  iU'si;:iie<l  piisli 
l)iitt(>n  that  can  he  (■(•nifortahly  liehl  in  the  liaml.  At  other  cml  tlie  conl  is 
i'<liiippe(l  with  a  suitahle  piii;:  adapted  for  altaciuucnt  to  peniiaiieiitly  installed 


FRONT  OF  POST  AND  BOX 

Fig.  7-5.— S.   A.   TARGET     RANGE.    TYPE    NO.    1     SYSTEM,    OUTLET    BOX. 


target  range  outlet  huxes.  The  push  hutton  referred  to  is  shown  in  tigiuv  7-1, 
and  the  round-pattern  target  range  outlet  hox  with  plug  is  shown  in  figure  7-2. 
The.se  boxes  have  been  more  or  less  unsatisfactory,  due  principally  to  the  fact 
that  the  screw  cap  covers  are  often  not  replaced  when  plug  of  push-button  cord 
is  withdrawn,  tliereby  allowing  moisture  to  enter  the  box. 

Figure  7-3  shows  an  outlet  box  designed  by  the  Signal  Corps  which  is  now 
being  given  a  service  test.  AN'itli  this  i)ox  there  is  no  screw  cover  to  be  remove*] 
or  replacjed  in  connection  with  the  operation  <tf  inserting  or  withdrawing  the 
plug.  When  plug  is  inserted  in  socket  on  ontside  of  box,  a  thin  metal  iliaphragm 
forming  side  of  box  is  depressed.  Two  insulated  contact  pieces  through  dia- 
phragm, which  make  contact  with  parts  of  plug  to  which  ctmductors  of  cord 
are  attached,  are  made  to  connect  with  suitable  terminals  of  cable  on  inside  of 
box  by  depression  of  diaphragm.  It  is  therefore  only  -necessary  to  remove  plug 
when  use  of  a  particular  outlet  is  c<nnpleted.  Removal  of  plug  allows  dia- 
phragm to  attain  normal  position,  thereby  breaking  contact  between  insulated 
pieces  through  diaphragm  and  terminals  of  cable  on  inside  of  box.  It  «-an 
readily  be  seen  that  siuface  leakage  of  battery  current,  due  to  moisture  on  out- 
side of  box.  is  eliminated  when  plug  is  withdrawn. 

For  illustrating  the  various  types  of  ranges  and  for  showing  the  equipment 
fin-nished  and  the  methods  of  its  installation,  type  ranges  are  shown  in  the 
following  figures.  In  future  it  will  probably  be  found  that  in  n«i  case  d<H>s 
the  range  exactly  conform  to  any  one  of  the  types  shown.  It  may  be  necessary, 
therefore,  to  modify  the  type  scheme  to  make  it  applicable  to  any  particular 
case. 

1269) 


6 


Signal  Corps  Manual  No.  3. — Chapter  7. 


Fijiuro  7-4  shows  the  typi'  1  sysleni  as  installed  on  a  ran,ii'e  eciuiitped  with 
12  targets  and  as  installed  on  a  range  equipped  with  24  targets.  Figure  7-.") 
shows  the  type  of  outlet  box  and  manner  of  coiuiecting  it  installed  at  eaeh 
liring  line,  and  tigure  7-G  shows  the  construction  of  a  portable  box  for  pro- 
tecting telephones  used.  In  jireparing  lists  of  material  for  installation  of  a 
type  1  system,  either  the  length  of  cords  for  ronnecting  \]\o  portable  tele- 
phones or  width  of  range  and  luunber  of  targets  nuisi  be  staled. 


Fig.  7-6.— S.  A.  TARGET  RANGE.  TYPE  NO.  1  SYSTEM,  TELEPHONE  BOX. 


I'Mgure  7-7  shows  a  typo  2  system  using  one  diminishing  si7,(>  caljle  laid 
iliagonally  across  the  range  with  tajts  to  tlie  vai'ious  butts,  while  figure  7-8 
shows  separate  cables  used  for  each.  Foi-  eclielon  ranges  eiUier  of  these 
methods  or  a  combination  of  the  two  may  l)e  used,  deiuMiding  ui»on  local  con- 
ditions: however,  whenever  i)i'acticable,  the  method  shown  liy  tigure  7-S  i.s 
|iref('i'i-c(|.  '{'he  scale  size  of  these  ilhistrations  is  such  that  it  is  imprai'licable 
(o  show  all  ai»paratus. 

Figure  7-9  siiows  a  ly|>e  :>  system,  ^^■ith  this  i)articular  system  the  2(M)-yard 
firing  points  were  not  ('([nipped  with  outlets  but  i)rovision  for  such  (Mpiiitnunit 
was  made,  (he  necessary  maidatles  on  line  of  main  cabl(>  having  been  i)rovided. 

Strap  l<c.\s,  annunciator,  and  master  switch  are  ))rovided  for  this  type  of 
range  in  or(lcr  tlint  standard  connnuiucat  ion  for  ra)»id-tire  jiractice  .at  (he 
2(K)-yard.  .'{OP-yanl.  and  .">(»( )-.\ar(l  firing  ])oints  will  be  available. 

Figure  7-1P  shows  the  method  employed  in  iiistiiHing  the  round  ii;itterii 
ontlet  boxes.  Sewer  Hush  jtipes  uilli  cover  are  used  to  house  tlie  outlet  box 
where  is  terminated  the  tyi>e  2."(1  c.-dile  (1  i)aii-  le;id  covered  and  armored). 
.\  wrought-iron  support  for  oulli'l  box  is  fastened  by  means  of  machine  screws 
1o  l)e]l  of  sewer  (lusii  pi])e.  Tlie  ty)ie  2.">1  cable  enters  the  outlet  box  through 
a  short  length  of  I  hree-fourlh  inch  conduit  threaded  tlinaigh  snpiiorl  sind  into 
base  of  outlet  box.  The  cable  is  sealed  by  tilling  the  conduit,  witinn  which  is 
terminal(^d  the  sheaths  of  cable,  with  ozite  or  other  approved  moisture  repellent 

(J70) 


Small-Arms  Target  Range  Signaling  Systems. — Chapter  7. 


T 


rr^ M^ iSXT-  \  3! 


fj^^m^f 


S.    A. 


TARGET    RANGE.    TYPE    NO.    2    SYSTEM.    USING    DIMINISHING    CABLE. 


Signal  Corps  Manual  No.  3.— Chapter  7. 


(272) 


Small-Arms  Target  Range  Signaling  Systems. — Chapter  7  [) 


TAROLT  BUTT3 


200  YARD  LINC 


0     o    o@o    o_  o 


0  g 


II  f:r'rii    points  lOOl. 

fQprcab^c  '  ^1  prorma  cable 


3  •? R 


tfOO  YARD  LINE 
13     Q      g      o@0      Q     9      o      o      o@o 


oosnts  aOQYAROUNE.  I2  hrir. 

O      O       O      0©0       O  O       OrS)©       O      O       O 


5fj!ght  J  njy  5pl<C£. 


^ ^ 


o    o     o®o    o     o 


o     otSio     o     o. 


>®o    o    o 


O      O  O^O      o 


LEGZNC 

K^anholc  Q 

Distribubng  box  ■ 
Spea'o/  7^y  Rr^Ju  «j  5tax     # 

TeJcphorc  % 

Buzzer  m 

Finnj  point  o 


o    o    o    o@o    o 


Fig.  7-9.— S.  A.  TARGET  RANGE,  TYPE  NO.  3  SYSTEM. 
(273) 


10 


Signal  Corps  Manual  No.  3. — Chapter  7. 


Scale-— 2  in=l  in. 


PLAN    WITH  COVER  REMOVEJD 

\ ^aV 


/8  th'ds  pr  in.   X  I  .  i-L-i. 
Tap   ^'deep        C\J  «*? 


Tap  standard  size 

for  -^'  pipe  -t4  f^rtls.  pr  i. 


— ■  \com1rfithin0 
— ^radiuidt^" 

I 


FiM  corners. 

^nMilsidtstont 
\:sy  mthin  4'ptpc 


SUPPORT  FOR   OUTLET  BOX 

One  for  eacti  box  — Wrot.  iron 


■  y  /4  t1l'ds.pr 


Fig.  7-10.- 


PIPE 

Standard  -^  inch 
Loricated   conduit 

A.  TARGET   RANGE,  TYPES  2   AND   3   SYSTEMS,   OUTLET   BOX,    INSTALLA- 
TION   OF. 

(274) 


Small-Arms  Target  Range  Signaling  Systems. — Chapter  7. 


11 


compound.  Installation  of  1915  model  outlet  box  is  similar,  the  box  being 
provided  with  supporting  lugs.  It  will  be  noted  that  the  sewer  flush  pipes  are 
equipped  with  a  substantial  removable  cover. 

Military  drills  by.  various  arms  of  the  service  are  sometimes  held  on  small- 
arms  ranges  and  with  outlets  installed  as  shown,  little  or  no  inconvenience  is 
occasioned  tlie  troops.  When  tlie  soil  is  soft  and  the  wheel  of  an  artillery  field- 
piece  comes  in  contact  with  one  of  these  flush  pipes  it  may  be  deflected  fi-om 
the  vertical  position,  but  no  injury  results  as  sower  flush  pipe,  outlet  box,  and 
sealing  chamber  are  moved  as  a  unit,  the  type  251  cable  being  flexible.  The 
pipes  are  easily  returned  to  correct  position  after  such  an  (x-currence. 


f  "■""■"r"\^^^^*v-^^'^"'^' i^ ^ 


Fig.  7-11.— S.    A.    TARGET    RANGE,    TYPES    2    AND    3    SYSTEMS,    MASTER    SWITCH. 

Figure  7-11  shows  the  construction  of  a  master  switch  for  a  range  having 
IG  targets.  These  switches  have  been  furnished  for  ranges  having  24  targets, 
and  while  they  can  l)e  made. for  a  greater  capacity  on  the  very  large  ranges, 
it  is  believed  advisable  to  install  two  switches,  arranged  to  be  operated  simul- 
taneously, if  desired. 

Figure  7-12  shows  construction  of  manliole  usually  used  in  connection  with 
buzzer  annunciator  system.  One  of  the.se  manholes  is  constructed  at  each 
flring  line  on  line  of  each  main  cable  witli  the  type  3  system.  With  the  type 
2  system  location  and  number  is  dependent  upon  local  conditions. 


(275) 


12 


Signal  Corps  Manual  No.  3. — Chapter  7. 


In  these  manholes  are  installed  the  target  range  junction  box  from  which 
tlistributiou  (b.v  means  of  type  251  cable)  of  circuits  to  outlet  boxes  is  made. 
It  will  be  noted  that  cover  of  manhole  is  (3  inches  below  surface  of  earth  so 
that  it  is  nnnotice<l  when  drills  on  range  are  held.  If  Artillery  drills  are  held 
on  range  it  is  advisable  to  provide  extra  support  for  boiler-plate  cover.     A 


PLAN 


Grouncf  /me 


jUJ 


h-  e'-H 


SECTION 


Fig.  7-12.— S.   A.  TARGET    RANGE,   TYPES  2   AND   3   SYSTEMS,    MANHOLE. 

siiiiill    .".inch    cycliciiiii    .'icrKSs    (•ciilcr    of    ni;iiilii>l('.    su)»i)(irli'd    Ity    inanliolt'    and 
removable  at  will,  is  an  excellent  nu'tliod  of  providing  this  extra  sui>p<)rt. 

I'Mgwrt"  7-  1.'?  sliiiws  tiic  cnMstrnctinn  of  tlic  target   range  junction  box,  usually 
installed     iti     nianlioics    jusi     desciihfd.      Snilsdilc    openings    are    provided     in 


C-'-Ci 


Small-Arms  Target  Range  Signaling  Systems. — Chapter  7. 


bottom  of  box  for  oiitrjiiicc  of  :i  lap  froin  maiii  cable  and  a  number  of  type 
2r)1  cables.  Tap  from  main  calile  enters  tbroii;,'h  circuhir  opening  and  t.vpe  2~A 
ral)le  tbroujili  (>loimateil  oixMiin^'s  on  eitlier  side  of  circular  opening.  Tbe  box 
will  accoiiiiiutdale  tliree  Sijiiial  Corps  standard  porcelain  terminal  strijis  U) 
wliicli  conductors  of  cables  are  connected  and  wiiere  proper  cross  connection 
can  be  made. 


Fig.  7-13.— S.    A.   TARGET    RANGE,    TYPES   2    AND    3    SYSTEMS,    TARGET    RANGE  JUNC- 
TION   BOX. 

Figure  7-14  sliows  the  construction  and  arrangement  of  equipment  of  the 
distributing  box  for  target  ranges.  This  box  is  installed  at  the  butts  and 
contains  the  20  cells  of  dry  battery  which  furnishes  current  for  operating  the 
buzzers  and  aimunciator  for  each  range.  This  box  also  contains  three  suitable 
conunercial  terminal  strips  to  which  are  connected  conductors  of  cal)le  to 
tiring  points  and  rubber-covered  wires  to  buzzers,  strap  keys,  annunciator, 
master  switdi,  and  telephone  at  butts.  Appropriate  cross  connections  of  the 
Aarious  lines  are  made  at  these  terminal  strips  with  No.  lU  rubber-covered 
wire. 

Figure  7-1.")  shows  the  manner  of  installing  the  l)uzzer  and  strap  Vcey.  The 
two  pieces  of  apparatus  are  mounted  on  a  hard  maple  backboard  providetl 
witli  brass  lugs  through  which  pass  the  screws  wliidi  fasten  it  to  parapet 
wall.  A  sheet-metal  cover  is  provided  for  protecting  tlie  buzzer  and  strap  key 
from  the  elements.  This  cover  is  held  in  position  by  fom-  brass  screws  in 
side  edges  of  maple  liackboard.  Tliese  screws  are  so  inserted  that  the  heads 
are  distant  from  backboard  the  thickness  of  metal  cover.  Slots  are  cut  in 
metal  cover  for  engaging  the  screws,  and  the  cover  can  be  placed  in  position 


(277) 


14 


Signal  Corps  Manual  No.  3. — Chapter  7. 


or  removed  without  removing  tlie  screws.  The  strap  key  can  be  operated  with- 
out removing  metal  cover,  as  there  is  an  opening  with  slide  cover  for  this 
purpose. 

While  a  number  of  strap  keys  and  buzzers  have  been  installed  in  this  manner, 
it  is  intended  that  in  future  a  small  metal  box  in  the  form  of  a  condulet  into 
which  the  three-fourth  inch  conduit  will  be  threaded  will  be  supplied  for  the 
purpose. 


JNT   WITH  Ooon  OPtN 

Fig.  7-U.— S.   A.  TARGET    RANGE,   TYPES  2    AND   3    SYSTEMS,    DISTRIBUTING    BOX. 

'riit'  standiii'd  iiictliod  of  wiriii;:  he!  wccii  Hit'  disi  ribiilin::'  Ixix  :w\d  llic  bu/./,er.s 
and  strap  keys  is  as  follows: 

lioricaled  fotidnit  from  dislribuliim  box  to  tlaiik  bu/z/crs  and  straj)  keys  is 
sccurt'ly  rastciiod  to  ijarajicl  w;ill.  liic  means  of  rasU'iiiiii;-  being  dependent  on 
iiiiiterlal  of  whieh  parajiet  wall  is  made.  This  line  ol'  conduit  is  below  the 
horizontal  plane  ()f  position  of  the  buzzers  and  strap  koys.     At  each  buzzer 

(278) 


Small-Arms  Target  Range  Signaling  Systems. — Chapter  7. 


15 


and  straji  key  tliis  coiKluit  line  is  j'l-ovidcd  witli  a  piiic  tee,  the  tap  open'uv^ 
heliiir  lor  three-fourth  iiu-h  eomluit.  A  piece  of  three-fourtii  inch  coiKhiit 
endinj;  on  a  liorizoiital  level  midway  between  buzzer  and  strap  key  is  threaded 
into  tap  openinj;  of  i)ii>e  tee  and  the  upper  end  of  this  conduit  should  be  sealed 
with  Chatterton  coniiuiund  after  wire  mentioned  later  has  been  pulled  in  the 
conduit. 


A.  TARGET  RANGE,  TYPES  2  AND  3  SYSTEMS,   INSTALLATION   OF  STRAP 
KEY   AND    BUZZER. 


Rubber  covered  and  braided  wire,  conductor  51  mils,  i.s  used  for  the  con- 
nections between  distributinjr  box  and  buzzer  and  .strap  keys.  This  wire  should 
be  pulled  in  the  conduit  simultaneously  with  tlie  placing  of  conduit,  as  the  wire 
can  not  be  pulled  around  the  sharp  corners  of  the  pipe  tees. 


(279) 


16 


Signal  Corps  Manual  No.  3. — Chapter  7. 


Figure  7-16  shows  a  diagi-am  of  through  circuits.  Referriug  to  this  figure 
it  will  be  seen  that  one  wire  is  common  to  center  post  of  all  strap  keys.  This 
wire  should  not  be  tapped  but  should  be  looped  to  center  binding  post  of 
each  strap  key.  the  loop  extending  from  pipe  tee  to  strap  key. 

The  size  of  conduit  for  the  main  rini  is  dependent  upon  the  number  of  tar- 
gets on  the  range  and  in  some  instances  it  may  be  advisable  to  use  two  or  more 
sizes,  reducing  the  size  as  distant  outlets  are  reached.  If  it  is  impracticable  to 
locate  the  distributing  box  near  longitudinal  center  of  parapet  wall  on  a  range 
having  30  or  more  targets,  cable  should  be  installed  between  distributing  box 


Fig.  7-16.  — S.  A.  TARGET   RANGE,  TYPES  2  AND  3  SYSTEMS,  THROUGH    CIRCUITS. 


and  one  or  more  can  terminals,  appropriately  located,  and  coinhilt  lines  extended 
iioni  can  terminals  to  buzzers  and  strap  keys.  Figure  7-17  illustrates  such  an 
arrangement.  It  is  also  applicable  under  some  conditions  where  the  miniber 
of  targets  exceeds  .50.  regardless  of  whether  or  not  distril)uting  box  be  locatecl 
near  longitudinal  center  of  parapet  wall. 

When  approved  in  each  individual  case  by  the  ('liief  Signal  Oflicer  of  the 
Ariny,  the  sniall-arnis  range  may  be  connc^cted  t«'lepli()nically  with  nearest  post 
tflei)hone  system. 

The  wiring  for  annunciator  and  master  switch  is  dependent  upon  coiulitions. 
In  some  instances  the  master  switch  is  mounted  on  the  side  of  the  distributing 
box,  In  the  event  of  which  it  is  only  necessary  to  make  a  neat  form  of  sufficient 
number  of  rubber-covered  wires  extending  tiie  wires  from  terminal  strip 
tlu'ough  sifje  of  box  t<»  master  switch.  If  the  master  switch  or  annunciator  are 
place<l  distant  from  distributing  box,  tin!  coiniecting  wires  should  be  iu  iroa 
conduit  of  suitable  size. 

(280) 


Small-Arms  Target  Range  Signaling  Systems. — Chapter  7. 


17 


As  funds  bocomo  available  for  the  construction  of  systems  corresponding  to 
types  2  and  3  special  plans  will  \h'  drawn  to  meet  the  varying  conditions  of  the 
ranges  that  may  bo  selected. 


Cal'te&sDa'r^buhn^  e<j* 


Fig.  7-17.— S.   A.  TARGET    RANGE,   TYPES  2   AND  3   SYSTEMS,    USE  OF  CAN   TERMINAL. 

For  some  of  the  large  ritle  ranges  the  Hignal  Corps  has  supplied  a  portable, 
direct-reading  anemometer.  The  use  of  these  instruments  is  confined  to  pre- 
liminary drills  for  instruction  in  wind  reading.  They  will  not  he  allowed  on 
the  range  during  the  regular  practice  season  or  during  competitions.  (M.  S. 
O.,  1201729.) 

KKCOKD.S. 

As  previously  stated  in  this  manual,  in  no  branch  of  the  industrial  field  are 
records  of  such  great  importance  as  those  pertaining  to  electrical  installations. 

The  Signal  Corps  requires  that  ui)on  completion  of  a  small-arms  target  range 
signaling  system  a  complete  and  accurate  record  be  prepared  by  the  person  in 
responsible  cliarge  of  installation  of  the  system. 

This  record  consists  of  standard  Signal  Corps  forms  appropriately  accom- 
plished and  drawings  illustrating  connections,  cross  connections,  routing  of 
cables,  and  location  of  manholes  and  location  of  apparatus.  All  prints  of 
tracings  and  page  8  of  Signal  Corps  Form  No.  211  are  submitted  in  triplicate  if 
range  is  for  the  United  States  Army  and  in  quadruplicate  if  for  the  militia. 
One  complete  copy  of  the  record  is  furnished  for  oflice  of  each  of  the  following 
oflicials : 

Chief  Signal  Ollicer  of  the  Army. 

Department  Signal  Otlicer  of  the  department  in  wliich  the  range  is  located. 

Commanding  Officer  of  post  to  which  the  range  is  attached. 

In  addition  at  least  one  copy  of  di  awing  shown  under  subheading  "a."  apiiear- 
ing  later  in  this  chapter,  shall  be  transmitted  to  the  local  post  (piartermaster 
that  he  may  be  familiar  with  location  of  Signal  Corps  cable  and  conduit  system. 

If  the  range  be  for  an  organization  of  the  militia,  the  latter  copy  and  an 
additional  one  should  be  forwarded  to  the  Chief  Signal  Officer  of  the  Army  for 
transmittal  to  the  Chief,  Division  of  Militia  Affairs,  General  Staff,  one  copy 
being  for  the  files  of  his  office  and  one  for  him  to  transmit  to  Adjutant  Gen- 
eral of  the  State  militia,  who  will  decide  its  custody. 

The  drawings  should  be  made  by  means  of  waterproof  ink  on  tracing  cloth. 
When  installation  of  a  system  is  made  by  the  Signal  Corps,  United  States  Army, 
and  it  is  impracticable  to  make  these  drawings  where  installation  of  system  is 
made,  the  data  should  be  forwarded  by  person  in  responsible  charge  of  the 
work  to  the  Department  Signal  (Officer  of  the  department  in  which  the  range 
is  located.  The  Department  Signal  Oflicer  will  have  the  tracings  made,  if  facili- 
ties are  available  in  his  office,  using  the  data  furnished  as  a  guide.     If  im- 

(281) 


18  Signal  Corps  Manual  No.  3. — Chapter  7. 

priK-ticable  to  make  the  drawings  in  tlie  office  of  the  Department  Signal  Officer, 
the  data  should  be  forwarded  to  the  Chief  Signal  Officer  of  the  Army  with  re- 
quest that  the  drawings  be  made. 

The  upkeep  of  these  records  is  important  and  all  authorized  changes  should 
be  recorded.  It  is  the  duty  of  signal  officers  to  see  that  all  moditications  of  the 
original  system  are  reported  in  order  that  the  tracings  may  be  revised  and  the 
various  offices  furnished  a  print  of  the  revised  tracing.  If  the  system  installed 
be  for  the  United  States  Army,  and  there  are  facilities  for  changing  the  draw- 
ings (tracings)  and  for  making  prints  in  the  office  of  the  Department  Signal 
Officer,  the  tracings  will  be  tiled  in  that  office,  otherwise  they  will  be  tiled  in  the 
office  of  the  Chief  Signal  Officer  of  the  Army.  If  the  system  installed  be  for 
the  militia,  the  custody  of  the  tracings  should  be  decided  by  the  Chief,  Division 
of  ^lilitia  Affiairs,  in  each  individual  case. 

Component  parts  of  the  recortl  required  are  as  follows : 

((/)  One  or  more  drawings,  map,  to  scale,  sliowing  routing,  type.  Signal 
Corps  number  of  reel  from  which  taki>n.  and  splices  of  all  cables  and  routing 
of  aerial  lines  if  there  be  any,  location  of  manholes,  and  all  apparatus  installed. 
If  conduit  for  cables  is  used,  the  kind  and  size  should  be  indicated.  The  dis- 
tance between  center  of  manholes  and  each  of  the  two  outlet  boxes  on  either 
side  should  be  accurately  shown  as  the  surface  indication  of  these  underground 
manholes  is  ofttimes  obliterated. 

(b)  Drawing,  diagram,  not  necessarily  to  scale,  showing  ail  connections  and 
cross  connections.  This  should  include  all  connections  and  cross  connections  in 
distributing  boxes,  all  connections  and  cross  connections  in  junction  boxes,  and 
an  outline  of  the  circuit.  A  statement  in  the  form  of  a  note  relative  to  average 
insulation  measurement  of  conductors  of  cable  should  appear  on  this  drawing. 
If  cables  contaiu  any  defective  conductors,  they  should  be  indicated  as  such. 
This  drawing  may  l)e  combined  with  drawing  described  under  (a)  if  crowding 
does  not  result. 

SIGNAL  COKl'S  FORMS. 

(r)  Signal  Corps  Form  No.  211  (report  of  inspection  of  Signal  Corps  equip- 
ment). The  lower  half  of  page  8  of  this  form  pertains  to  rille-range  ecpiip- 
ment  and  should  be  accomplished  for  each  copy  of  the  record  by  pers(Mi  in  re- 
sponsible charge  of  an  installation. 

{(l)  Signal  Corps  Form  No.  282  (cost  data  of  target-range  system).  This 
form  should  be  accomplished  in  duplicate  (regardless  of  whether  the  system  be 
for  United  States  Army  or  militia)  by  person  in  responsible  charge  of  installa- 
lion  of  the  system.  One  copy  is  for  the  files  of  the  Chief  Signal  Officer  of  the 
Army  and  one  for  the  files  of  the  Department  Signal  Officer  of  department  in 
which  range  is  located. 

On  large  ranges,  when  sullicient  funds  are  available,  the  longitudinal  cables 
slu)uld  either  Ik;  armored  or  plac(>d  in  conduit,  the  former  being  preferable.  A 
number  of  systems  using  plain  lead-covered  cable  trenched  have  been  put  out  of 
fonnriission  by  gophers  gnawing  through  lead  sheath.  The  same  lias  hai>j)ened 
with  plain  lead-covered  cahlc  in  coiiduit  wlicro  conduits  were  not  sealetl  at 
manholes.  Where  plain  lead-covered  cable  is  used,  every  i>r<><-aution  should  \w 
employed  to  prevent  rodents  entering  the  conduit  system,  for  while  this  trouble 
ajiparently  is  not  exjM'rienced  in  cities  and  at  most  Army  posts  it  has  actually 
occurre(l  in  the  Philiintine  Islands  and  at  .some  places  in  continental  United 
Stales.  The  liiteral  cables  from  target-range  junction  boxes  to  push-button 
outlets  should  invariably  be  type  2.'')1  (one  i)air  lead-covered  and  armored), 
and  trenched. 

(281' J 


Chapter  8. 
technical  equipment  issued  by  the  signal  corps. 

This  (liapttT  is  devoted  t(»  :iii  eimineratioii  of  latest  technical  equiitiiiciit 
issued,  with  brief  description  of  various  items.  It  is  prepared  with  a  view  of 
assisting  in  the  preparation  of  re(iuisitions. 

For  description  of  items  representing  apparatus  for  fire-conti'ol  systems  at 
seacoast  defenses  the  reader  is  referred  to  Signal  Corps  Manual  No.  8,  revised 
edition. 

Information  relative  to  the  cost  of  material  listed  may  be  ol)tained  from 
the  current  Signal  Corps  price  list  issued  annually  at  the  beginning  of  the 
fiscal  year. 

The  technical  equipment  issued  inclmles  the  following : 
Alcohol : 

Denatured. 

Wood. 
Anchor,  expansion,  bolt,  shield  |  by  2  inches,  screw  f  by  3  inches  (without  lag 

screws). 
Anchors,  expansion,  screw : 

1-inch,  without  screws,  for  Xos.  9,  10,  and  11   wood  screws. 

If-inch.  without  screws,  for  Nos.  9,  10,  and  11  wood  screws. 

2-inch,  without  screws,  for  Nos.  9,  10,  and  11  wood  scx*ews. 
Anemometers,  i)ortab!e.  with  tripod  and  cups. 
Anemometer  stop  watch. 
Annunciators,  target  range :  ' 

10-signal. 

20-signal. 

25-signal. 
Ardois  lights,  sets,  complete : 

Globes,  tolophoto,  for  Ardois.     Specify  whether  red  or  white  and  name  of 
manufacturer  of  set. 
Arresters,  Mason,  fused : 

Coils,  choke,  with  carl)on  blocks  and   mica  insulators,   in   pairs. 
Asbestos,  sheet  (thickness  to  suit  requirements). 
Axes : 

Helves  for. 
Axes,  hand : 

Handles  for. 
r.ags,  tool,  .service.     (See  i>.  (IS,  this  ch.-ipter.) 
Bars,  digging  and  tamping. 
Barometers : 

Aneroid. 

Mercurial. 

Box,  wooden,  for. 
46581°— 17 19 


(283) 


2  Signal  Corps  Manual  No.  3. — Chapter  8, 

Batteries : 
Dry- 
Miniature. 

No.  4-0,  Reserve  type. 
No.  6,  Reserve  type. 
Tunjisten,  type  A  (2-cell  units). 
Edison  primary  battery,  type  V — 
Complete. 

Renewals  for,  complete. 
Jars  for. 
Covers  for. 
Fuller- 
Complete. 
Jars  for. 
Porous  cups  for. 
Covers  for. 
Carbons  for. 
Zincs  for. 
Chromac  for. 
Mercury  for. 

Gaskets,  rubber,  for  cover  of. 
Gravity,  5  by  7  inches,  main  line — 
Bluestone. 
Coppers  for. 
Jars  for. 
Zincs  for. 
Storage — 

Type  A,  1.5-cell  (10-ampere  rate). 
Type  K,  l.^-cell   (15-anipere  rate). 
Type  ET,  coupled  (4i-anipere  rate). 
6-volt,  80  auii)ere  hours  (for  audion  detectors). 
Maintenance  parts — 

Electrolyte,  1.200  S.  G.    (120-11).  carboy). 
Electrolyte,  1.400  S.  G.    (120-lb.  carboy). 

Carboys  for  (not  included  in  the  above). 
Elements,  negative  (for  10-ampere  rate). 
Elements,  positive   (for  10-anipere  rate). 
Hydrometer. 

Insulator,  glass,  petticoat,  for  tray. 
Jars,  glass. 

Jars,  rubber,  with  covers. 
Plates,  positive  or  negative. 
Separators. 
Syringe,  hard-nilihiT. 
Thermometer,  lloatiiig  tyi)e. 
Trays,  sand   (for  10-ampere  rate). 

XoiE. — In   requesting   iiny   i)arts   for   storage  batteries,   the 
manufacturer,  type,  and  any  other  relative  data  nnist  l)e  sup- 
plitMJ,  in  order  that  the  i)roper  parts  may  be  supplied. 
P.eeswax. 

I'.ellows,  motor  {generator. 
P.olls,  exten.sion,  loud  ringing,  with  condenser.     (Set;  p.  22,  this  chapter.) 

(284) 


Technical  Equipment  Issued  by  the  Signal  Corps. — Chapter  8. 

Belts,  liiu'maM'.s  tool,  with  rings  and  sulety  sti'aps. 
Bicycles,  chain. 
Blanks,  telegraph : 
Message  i*eceived. 
Message  sent. 
Blotters,  small. 
Blocks : 

Connecting,  W.  E. — 

6A  (7-pair). 

7A  (1-pair). 

6B  (11-pair). 

6C  (IG-pair). 

GD  (21-pair). 
Ternjinal,  telephone. 
Boards,  letter  clip. 
Bolts : 

Expansion   (see  Anchors). 

Carriage  (for  securing  brace  to  cross-arm),  §  by  4  inches. 

Lag  (for  securing  brace  to  pole).     (See  Screws,  lag.) 

Cross-arm  (for  securing  cross-arm  to  pole)    (give  length  desired)  — 

f  by  10  inches. 

f  by  12  inches. 

f  by  14  inches. 

f  by  16  inches. 

f  by  18  inches. 

I  by  20  inches. 
Machine   (give  length  and  size)  — 

f  by  6  inches. 

s  by  8  inches. 

§  by  10  inches. 

i  by  12  inches. 
Stove   (give  length  and  size)  — 

s  by  2  inches. 

i  by  4  inches. 

i  by  6  inches. 

i  by  8  inches. 
Toggle  (give  length  and  size)  — 

i  by  3  inches. 

i  by  6  inches. 
Books,  field  message   (Form  217.\). 
Boxes  (also  see  p.  20,  this  chapter)  : 
Connecting. 
Distributing. 
Junction,  iron. 
Outlet,  circular  type — 

Bases,  porcelain,  for. 

Gaskets,  for. 

Plugs  for,  with  8-foot  cord,  with  lignum-vit^e  tips. 

Supports  for. 

Without   plugs. 
Outlet,  marine  type,  complete  with  plugs. 
Cable  pole.  Sterling,  complete,  with  tubular  fuses  and  carbon  arresters. 

(285) 


4  Signal  Corps  Mzinual  No.  3. — Chapter  8, 

Boxes — Cou  t  iuued . 
Cut-out,  2-.switch. 
Cut-out,  3-s\vitch. 
Junction,  iron,  3-way. 
Outlet,    searclilight. 
Switch,  base  line. 

Terminal,  fire-control  type  (see  p.  20,  this  chapter)  — 
2-strip,  metal,  1915  model. 
4-strip,  metal,  1915  model. 
8-strip,  metal,  1915  model. 
Transfer,  switch — 
2-sAvitch  type. 
4-switch  type. 
Time-interval  bell. 
Terminal,  submarine — 
Type  No.  1. 
Type  No.  2. 
Type  No.  3. 
Type  No.  4. 
Braces,  cross-arm  (IJ  inches  wide,  -^  inch  thick;  sive  lenjrth  desired)  : 
20-inch. 
22-inch. 
24-inch. 
26-inch. 
28-inch. 
Brackets : 

Iron,  for  lance  poles. 
Oak,  for  glass  insidators. 
Brushes,  paint,  all  sizes  (give  size  and  whether  round  or  flat). 
Buckets,  water,  canvas. 
Buttons : 
Push— 

Leather  cover  for. 
Buzzers,  Faraday  type,  150-ohm: 

Covers  for. 
Buzzer,  service,  model  1914   (the  1914  service  buzzer  when  furrn'slied  complete 
consists  of  1   buzzer  with  dry  balleries.  tools,  conncH'ting  cord.  i)lug,  tyiH'  A 
connector    fWilliains's    test    clamp),    transmitter    and    I'eceiver,    and    type    I> 
ground  rod). 
I'nzzer.  service^,  model   1914 — iiiaiiihMiancc  iiarls; 
Flatteries,  dry.  tungsten.  tyi)e  A. 

r.lock,  connecting,  for  condensei's,  complete,  assembled. 
Buttons — 

Hard  nihlier.  for  key. 
Transmitter  switch. 
Caps — 

Receiver. 
Transmitter. 
Coil,  complete,  witji  back  irons  and  bracket,  witlioiit  contact  screw,  mount- 
ings, and  vibrator. 
Condensers. 
Connector,  type  A   (see  p.  89,  tins  cliai>ter). 

(28«) 


Technical  Equipment  Issued  by  the  Signal  Corps — Chapter  8.  T) 

r.uzzcr.  scrvico,  model   1014   -< 'mil  iiiuod. 
Cords — 

Main,  witli   it'niiiuals. 

'I'l'jinsniillci-    and    rcccivcf    (atso   for   rooeivor   of   Field    Artillery    tele- 
phone ) . 
Cups,  fiber,  for  plugs  (also  for  plugs  of  Field  Arlillei-\   ti  leidione). 
iJoors.  battery,  eomplete.  with  liinges,  contacts,  and  covers. 
Headbands,  receiver  (also  for  I'McId  Artillery  telephone). 
Key,  lever,  complete. 

Supports  and  screws. 

Screws,  fulcrum. 

Screws,  platinun-  contact,  for  key  handle. 

Screws,  platinum  contact,  undei-  key.  auxiliary. 

Screws,  platinum  contact,  under  key,  main. 
Latches,  washers,  and  screws. 
Nuts,  hexagon,  for  base  wiring,  4-36. 
Plugs,  complete. 

Jacks,  plug  seat. 

Springs,  for  .jack. 

liods,  steel,  for  plug. 
Posts,  binding. 
Receiver,  with  headband  and  cords. 

Diaphragm  for. 

Cap  for. 
Screws,  adjusting,  with  platinum  contact,  for  vibrator. 

Adjusting. 

Clamp,  hlister  head,  ij-inch,  5-40.  for  vibrator. 
Spring  and  support. 

Battery  contact,  right. 

Battery  contact,  left. 
Spring  and  piece  for  condenser. 
Spring,  for  key. 
Straps,  carrying,  complete. 
Switches,  lever,  complete,  for  receiver. 
Transmitter,  with  cords,  complete. 

Diaphragm,  for  transmitter. 
Vibrator,  complete  (11  pieces). 

Washers,  micanite  (or  mica)  for  back  of  transmitter  case. 
Wrt'nches.  socket,  complete,  with  screw  driver. 
Cabinets : 

File,  storekeeper's. 
Supply. 
Terminal. 
Cables,  all  types  (for  complete  list  see  p.  2:i,  this  chapter:  for  description  and 

detailed  characteristics  see  chapter  4). 
Cables,  submarine,  gear  and  supplies  (see  p.  30,  this  chapter). 
Candles,  for  folding  candle  lantern. 
Cans : 

Gasoline,  1-gallon  size. 
Oil,  steel,  pint  size. 
Oil,  10-inch,  bent  spout,  copper. 
Cards,  code,  semaphore. 

(287) 


6  Signal  Corps  Manual  No.  3. — Chapter  8. 

Carriers,  wire,  for  buzzer  wire  {.see  p.  87,  this  chapter). 

Covers  for. 
Cartridges  (for  Very  pistols). 

Very — 
Green. 
White. 
Red. 

Smoke  (for  day  use). 
Carts,  signal.     (See  p.  23,  this  chapter.) 
Carts,  Avire.     (See  p.  33,  this  chapter.) 
Case: 

Battery  (for  holding  6  type  A  tungsten  dry  batteries). 

Map. 
Case,  electrical  instrument,  complete.     (See  p.  54,  this  chapter.) 
Cases,  reagent,  for  testing  storage  batteries. 
Cells,  dry.     (See  chapter  1.) 
Cement,  rubber,  2-pint  cans. 
Charges,  carbide,  for  field  acetylene  lantern. 
Chests,  tool : 

Aeroplane.     (See  p.  58,  this  chapter.) 

Construction.     (See  p.  62,  this  chapter.) 

Cable  splicer's.     (See  p.  64,  this  chapter.) 

Electrical  engineer's.     (See  p.  60,  this  cliapter.) 

Mechanic's  No.  1.     (See  p.  55,  this  chapter.) 

Mechanic's  No.  2.      (See  p,  5.5,  this  cliapter.) 

Pipe  fitter's.     (See  p.  65,  this  chapter.) 

Post.     (See  p.  66,  this  chapter.) 
Chisels,  cold,  6-iuch. 

Circuit  breaker  (circuit  breakers  are  furnished  as  a  part  of  the  various  power 
switchboards,  and  in  requesting  repair  parts  state  whether  single  or  double 
pole,  capacity,  overload  or  underload,  or  reverse  current,  manufacturer's 
name,  type  and  code  number,  and.  If  practicable,  catalogue  number)  : 

Double  pole,  overload  and  reversite  breaker,  calibrated  35-70  amperes. 

Tyi)e  E.  L.,  single  pole,  plain  overload,  rated  20  amperes. 
Clamp,  splicing. 
Clamps : 

Cable,  large. 

Cable,  small. 

Ground. 

(iuy,  2-l)olt. 

Guy,  3-bolt.      > 
(!leats : 

Porcelain,  1-wire  (for  inside  wiring  for  t('le])hones). 

I'orcelain,  2-wire. 

Porcelain,  3- wire. 

Wood,  cross-arm. 
Climbers,  willi  straps,  pairs. 
Clii)s: 

'i'cstliig. 

<'rosl)y,   3-iii'h. 
Clocks,  alarm. 


(288) 


Technical  Equipment  Issued  by  the  Signal  Corps. — Chapter  8.  7 

Cloth : 

Crocus,  sheets. 

Emery,  No.  00  to  No.  1*,  sheets — 
No.  4. 
No.  14. 
Coal  oil. 
Coil,  repeatinfr. 
Coil,  retardation. 

Compound,  Cliatterton's.     (See  p.  4;",  this  chapter.) 
Compass,  pocket. 

Condensers    (the  type  of  condenser,  manufacturer,  and  type  of  equipment  for 
which  it  is  required  should  be  stated)  : 
Western  Electric  No.  21 F,  for  common  l)attery  telephones. 
2-microfarad. 
8-microfarad. 
Conduit  (also  see  p.  43,  this  chapter)  : 
Bituminized  fiber — 
2-inch. 
2^inch. 
3-inch. 

Compound  for  joints. 
Flexible,  Greenfield — 
i-inch. 
f-inch. 
1-inch. 
Loricated — 
J-inch. 
1-inch, 
li-inch. 
2-inch. 
2i-inch. 
Elbows  for — 
1-inch. 
14-inch. 
2-inch. 
2i-inch. 
Condulets.  pipe,  F.  P.,  J-inch. 
Connectors : 

Type  A,  main  cord  of  st-rvice  buzzer  (see  p.  89.  this  chapter)  — 
Studs  for.  19-point. 
Terminal,  for  cord. 
Cord : 

Antenna,  42-.strand    (for  radio  masts). 
Sash— 

A-lnch,  No.  6  ((66  feet  to  pound). 
1-inch,  No.  12  (20  feet  to  pound), 
i-inch,  No.  5  (20  feet  to  pound). 
Buzzer,  main    (for  .«;ervice  buzzers). 
Tiamp — 

No.   14,   reenforced. 
No.  16,  reenforced. 
No.  18,  reenforced. 
(P'or  various  kinds  of  electrical  apparatus  cords  see  p.  35,  this  chapter.) 

(289) 


8  Signal  Corps  Manual  No.  3. — Chapter  8, 

Cotton,  striiis,  rolls,  for  cable  splicing.  10-yard  rolls. 
( 'ovei's  : 

<':iii\as.   teU'iiliiine  motor  generator. 

Ilandholc. 

Iron,  manhole,  44  by  30  by  g  int-li  (140  pounds  each). 

For  wire  carriers. 
Crank,   reel   cart. 
Cross  arms : 

For  iron  poles,  complete  with  bolts. 

Wooden,   2  to  10  pin,   bored  for  IJ-inch  pins    (state   number   of   pins   re- 
quired)— 
2-pin. 
C-pin. 
10-pin. 

Braces,  galvanized  iron,  20  to  28  inch  lengths,  for  (state  length). 
Braces,  galvanized  iron,  28-inch,   for. 
Cut-out,  porcelain,  wall   (main  or  branch,  in  sizes  to  suit  requirements;  give 

carrying  capacity  of  fuse). 
Disks,  cipher. 
Envelopes : 

Message. 

Penalty. 
Equipment,  lighting,  for  F.  C.  switchboard  rooms. 
Erasers,   rubber. 
Fault-finder,  Leeds  &  Northrup. 
Files,  property  return. 
Flashlights,  electric,  complete. 

Batteries  for  (tungsten,  type  A). 

Bulbs  (lamps)  for   (Mazda  "A"). 
Frame,  name  plate.  No.  2,  with  celluloid  cover. 
Fuses  (also  see  p.  42,  this  chapter)  : 

For  Mason  arrester,  1  ampere  ( type  9 ) . 

Cook,  type  A7,  5  amperes. 

Cook,  type  A12,  3  amperes. 

Type  1.  5  amperes. 

Type  1. 10  amperes. 

Type  2.  .^  amperes. 

Type  2.  10  amperes. 

Type  3,  .'>  amperes. 

Type  3, 10  amperes. 

Type  3. 1")  amperes. 

Type  3,  20  amperes. 

Type  3,  2.^  amperes. 

Type  3,  30  amperes. 

Type  4.  31  amperes. 

Type  II.  1  aniixTc  (  for  Mason  arrester). 

For  Sterling  Xo.  247E  i)rotectors,  i")  amperes. 

\V.  E.,  type  3r)r..  r*  amperes. 

W.  E.,  type  7A,  3  amperes. 
Gasoline. 


(290) 


Technical  Equipment  Issued  by  tlie  Signal  Corps. — Chapter  8.  9 

Glasses,  field. 

Type  A,  with  case. 

Case  for. 
Type  B,  \\ith  case. 

Case  for. 
Type  C,  with  case. 

f 'ase  for. 
Type  D,  with  case. 

Case  for. 
Type  EE. 

Case  for. 
Description  of  each  of  these  field  glasses  will  be  found  on  pages  40  and  41, 
this  chapter. 
Grips,  Buffalo,  No.  1,  Willi  ])nlleys. 
Hammers,  cari)enter's. 
Hand-set  switch,  1  liey. 
Hand-set  switch,  2  keys. 
Handles,  pay-out. 

Hangers,  cable,  galvanized  iron,  2-incli.  with  n  hooks. 
Hatchets. 

Handles  for. 
Heliographs,  complete,  with  two  tripods. 
Maintenance  parts- 
Cases — 

Leather,  carrying. 
Wood,  for  mirror. 
Frame  and  mirror,  complete. 
Heads,  tripods,  for  mirror  bar. 
Keys  with  bars  for  screen. 
Mirror,  field. 
Points,  steel,  for  tripods. 
Rods,  sighting. 
Screens,  complete. 
Screw  drivers. 
Screws — 

Adjusting,  with  clamps,  for  mirror  frame. 

Center,  for  tripods.  ' 

Tangent,  for  mirror  bars. 
Shutter,  complete. 
Springs,  mirror  bar. 

Tripods,  each  (2  furnished  with  heliograph). 
Hoods,  metal,  for  buzzer  and  strap  key. 
Hooks,  message. 
Houseline. 

Ink   (writing  fluid),  pints. 
Insulatine. 

Insulating  conijjounds.      (See  p.  44,  this  chapter.) 
Insulating  materials.     (See  j).  44.  this  chapter.) 
Insulators : 
Chuup. 
Pigtail, 

(291^ 


10  Signal  Corps  Manual  No.  3. — Chapter  8. 

Insulators — Continued. 
Glass — 

Double  groove. 
Double  petticoat. 
Pony. 

Transposition. 
Pony,  porcelain,  double  groove. 
Knobs,  porcelain   (give  si2e)  — 
No.  4. 
No.  5. 
NO.-14. 
Iron,  strap. 
Jack,  wagon. 

Jacks,  cable  reel  (state  lifting  capacity  desired)  : 
5-ton. 

Axles  for  (give  diameter  and  length). 
Axles,  2  inches  by  6  feet,  for. 
Keys : 

Strap,  with  slate  base.     (See  p.  43,  this  chapter.) 
Telegraph,  leg  or  legless,  open  or  closed  circuit. 
Kits: 

Flag- 
Combination,  standard   (consisting  of  1  case,  canvas;  1  staff,  3-joint; 

1  flag,  red,  white  square;  1  flag,  white,  red  square;  2  staffs,  sema- 
phore; 2  flags,  semaphore,  standard). 

Combination,  Artillery  (same  as  "  combination,  standard,"  except  that 

2  flags,  semaphore.  Artillery,  are  substituted  for  the  2  flags,  sema- 
phore, standard). 

Combination,  Infantry   (same  as  "combination,  standard,"  except  that 
1  Infantry  flag  is  substituted  for  the  2  red  and  white  flags). 
Maintenance  parts — 
Case,  canvas. 
'Staff,  3-joint  complete — 
Lower  joint. 
Middle  joint. 
Upper  joint. 
Staff,  semaphore. 
Flags — 

Red,  white  square. 
White,  red  squavre. 

Semapliore  (combinalion  or  Artillery). 
Infantry  (regular  organization). 
Infantry   (militia). 
Flag,  4-foot,  complete. 
Maintenance  parts — 
Case,    canvas. 
Staff,  3-j()iiit,  complete, 
liower  joint. 
Middle  joint. 
,  TTppor  joint. 

Flags— 

Ucd,  white  square. 
White,  red  square. 

(202) 


Technical  Equipment  Issued  by  the  Signal  Corps. — Chapter  8.  1 1 

Kits— Continued. 

Inspector's  pocket,  complete  (lor  full  description  see  p.  69,  tliis  chapter). 

^Maintenance  parts — 
Cases,  leatlier. 
Files,  3-inch. 
Knives,  electrician's. 
Pliers,  5-incli,  side-cutting,  nickeled. 
Rules,   2-foot. 
Scissors,  electrician's. 
Screw  drivers. 
Tweezers. 
Knives : 

Brush  cutting. 
Electrician's. 
Lacquer,  transparent,  ^-pint  tins. 
Lamps,  battery  examining,  2()-volt,  Edison  base. 
Lanterns : 

Acetylene,  field,  complete,  without  tripods    (tripods  furnished  with   helio- 
graphs are  used). 
Maintenance  parts — 

Base,  complete,  with  key. 
Burners  for. 
Bushings,    water-tube. 
Caps — 

For  inlet  tube,  with  needle  point. 
For  safety  outlet,  without  holes. 
Generator,  with  gooseneck. 
Cases. 

Charges,  carbide. 
Cleaners. 
Cocks,  gas. 

Covers,  complete,  with  front  glass. 
Diaphragms  for  carbon  holder. 

Gasket,  rubber,  for  top  and  bottom,  cartridge  opening. 
Generator,  complete. 
Glass,  front,  complete. 
Hose,  rubber. 
Lead,  white,  tubes. 
Lens  (see  Glass). 
Mirrors,   reflecting. 
Needles,    for    cleaning   burners. 
Pliers,  gas,  6-inch. 
Screw  driver. 
Springs — 

Key,  new  style. 
Key,  old  style. 

For  holding  carbide  cartridge. 
Stopper,  rubber. 
Straps,  carrying. 
Tips,  lava. 
Tripods,  each    (not  furnished  with  :uetylene  lantern;  use  one  of 

two  with  heliograph. 
Tubes,  outlet,  with  screw  caj)  and  gas  cock. 
(293) 


12  Signal  Corps  Manual  No.  3.— Chapter  8. 

Lanterns — Continued. 
Candle,  folding. 
Candles  for. 
Coal  oil. 

Globes  for. 
Wicks  for. 
Lead,  red. 

Leather,  strips,  for  pot  heads,  2i  by  6  inches,  sole. 
Line  construction  tools.     (See  p.  01,  this  clinpter.) 
Line  construction  materials.     (See  p.  45,  this  cliapter.) 
Loom,  'circular   (give  inside  diameter)  : 
f-inch. 
f-inch. 
Lugs,  for  terminals  (give  size  of  hole  for  conductor). 
Magneto,  testing  set,  lineman's. 
Map  measurers,  watch  style. 
Matches,  wind,  boxes. 
Megaphones.     (See  p.  89,  this  chapter.) 
Molding,  type  A.     ( See  p.  70,  this  chapter. ) 
Molding,  type  B.     (See  p.  70,  Ihis  chapter.) 
Mortars. 
Motor  generators : 

i-kilowatt  direct-current  motor    (for  charging  a  1.5-cell  telephone  storage 

battery ) . 
1-kilowatt  direct-current  motor   (for  charging  a   lo-cell   telephone  storage 

battery ) . 
Ringing,    direct-current    motor     (for    use    in    connection    witli    teleplione 
switchboards). 

Note, — These  machines  can  lie  furnished  Avith  either  direct-current  or 
alternating-current  motors.  When  requesting  alternating-current 
equipment  give  voltage,  frequency,  and  number  of  phases.  In  re- 
questing any  parts  give  manufacturer's  name,  type,  serial  number, 
size,  and  all  other  data  usually  shown  on  name  plate  of  ihe  machine 
for  which  the  parts  are  required. 
Maintenance  parts — 
Bellows  for. 

Brushes,  generator  side   (give  accurate  dimensions). 
Brushes,  motor  side  (give  accurate  dimensions). 
Busliings,  p(trcelain,  for  l)rusli   liolders. 
Motor,  starting  l)ox.     (Repair  parts  may  l>e  had  for  any  of  the  motor  starters 
furnished  by  the  Signal  Corps,     In  re(|uesting  these  parts  give  manufacturer's 
name,  type,  size,  and  serial  number;  ai.so  state  fully  Uie  part  desired  in  order 
to  obviate  mistakes.) 
Mountings,  buzzer,  target  range. 
IMountings,  n'tardation  coil. 
Mucilage,  bottles,  quarts. 
Muslin,   bh'aclicd,   yards. 
Nail  puller. 
Nails   (give  size  and,   if  wirc^  nails,  stale  \\h('nier  conunon,  finishing,  or  brad 

nails  are  refpiired). 
Oil,  dynamo. 
Oiling  sets,  complete. 
Ozite, 

(294) 


Technical  Equipment  Issued  by  the  Signal  Corps.— Chapter  8. 

Pads,  hand,  leather. 
Paint : 

MoKul,  prc'sorvative.     (See  p.  71,  this  cliupter.; 

Keady-mixed  oil  colors. 
Panel : 

Telephone,  power,  style  1. 

Telephone,  power,  style  3. 

Station  switch,  without  mountings.  ^ 

Paper : 

Carbon,  sheets. 

Legal  cap,  reams. 

Letter,  typewriter,  heavy,  reams. 

I>etter,  typewriter,  light,  reams. 
I'arafHn,  pounds. 
I'asters,  splicing,  2-inch. 
Paul  ins,  for  wire  carts. 
Pencils : 

Copying. 

Lead. 
Penholders. 
Pens,  gross. 

Photography.     (See  p.  72,  this  (•liai)ter.) 
Pick,  7-pound,  with  handle. 

Handle  for. 
Pikes,  wire.     (See  p.  89,  this  chapter.) 

Hooks  for. 

Poles  for. 
Pins,  cones. 

Pins,  insulator,  for  cross  arms,  11-inch. 
Pipes,  sewer  flush,  with  cast-iron  covers. 
Pistols,  A'ery. 

Cartridges  for.  red.  green,  or  white  (see  Cartridges). 
Pliers: 

.5-lnch,  side  cutting. 

8-inch,  side  cutting. 
Plow. 

Plugs,  insulator,  for  ii-oii  ]H)les,  oalc,  2-iMch. 
Poles,  lance.     (See  p.  89,  this  cliai)ter.) 

Insulators  for   (clamp  or  pigtail). 
I'oles,  telegraph  : 

Steel. 

Wood    (state  luMgiit   rtMiuired). 
I'sychromctcr,  sling. 
Kadio  equipment : 

Table  set,  i  kilowatt,  without  generator. 
Component  parts  for — 

Ammetei".  0—4  amperes. 

Angles,  set  of  8. 

Blocks,  wooden,  set. 

Box,  motor  starting. 

Bushings,  hard  rubber,  set  of  9. 

Button,  push. 

Buzzer,  test. 

(295) 


]4  Signal  Corps  Manual  No.  3. — Chapter  8. 

Radio  equipment — Continued. 

Table  set,  ^  kilowatt,  without  generator — Continued. 
Component  parts  for — Continued. 

Condenser. 

Cover,  canvas. 

Crystals,  for  detector. 

Gaps,  spark. 

Key,  sending. 

Padlock  and  hasp. 

Receiver,  telephone,  double  head. 

Receiving  set,  complete. 

Rods,  high  resistance. 

Switcb,  control. 

Switch,  lightning. 

8witcli,  snap. 

Table. 

Tran.sfornier,  oscillating. 

Transformer,  power. 
Motor  generator,  alternating-current  nuitor. 
Motor  generator,  direct-cun-ent  motor. 

Radio  pack  sets,  model  1915,  consist  of  the  following  units: 
1  operating  chest. 
1  hand  generator. 
1  mast ,  type  F. 
1  pack  frames,  set. 
1  tent. 
Each  unit  contains  component  partts  as  follows: 
Operating  chests — 

1  chest. 

1  resonance  transformer. 

1  condenser. 

1  o.scillation  transformer. 

1  sending  key. 

1  spark  gap. 

1  hot-wire  ammeter. 

1  switch. 

1  receiving  set. 

1  connecting  cord  for  generator  (4-conductor,  witli  plugs). 

1  connecting  cord,  with  plug,  for  antenna. 

1  double-head  receiver. 

1  test  buzzer. 

1  tool  kit. 

1  extra  section  for  transformer  sei'ondary. 

1  extra  set  crystals. 

1  canvas  case  for  receiver. 

1  connector,  4-wire  (lower  half),  geiicralor. 

2  connectors,  2-wire  (lower  half),  nntcnua  an<l  counlerpoise. 
1  flexible  comiector  for  antenna   inductance.* 

1  <'onnector,  2-wire,  small,  for  receiving  set.' 

2  spring  hooks.' 
4  legs  for  chest.* 

1  Supplied  wltli  1 1  •!   lOI.''.  cliost  only. 

(296) 


Technical  Equipment  Issued  by  the  Signal  Corps. — Chapter  8.  If) 

Radio  equipment — Continued. 

Each  unit  contains  component  parts  a.s  follows — Continued. 
Operating  chests — Continued. 

1  copy  '•  Kadiotelegraphy  "   (S.  O.  Cir.  No.  1,  1914,  revised). 
Hand  generator — 

1  generator. 

2  cranks. 
1  stand. 

1  speedometer  (carried  in  operating  cliest). 
1  cap  for  speedometer  opening. 
1  canvas  hood. 
Mast,  type  F.     Cl'yiM'  I)  mast  has  I  top,  1  h(»tl(iiii,  .">  intermediate  and 
3  extra  sections.)  — 
1  top  section. 
1  bottom  section. 

8  intermediate  sections. 

4  intermediate  sections,  extra    (3  for  tent). 
1  antenna. 

1  counterpoise. 

9  carriers,  wire. 
4  pins,  antenna. 

2  hammers. 

1  set  adapters  for  tent  (4  pieces). 
1  bag,  antenna,  and  counterpoise. 
1  bag,  accessories. 
Pack  frames,  set — 

3  frames   (1  set).     Each  frame  is  complete  with  cincha,  2  straps 
with  snap  hooks,  and  2  plate  staples. 

Tent— 

1  tent. 
14  pins. 

2  gny  ropes. 

1  insulating  device. 

Complete   radio   pack   sets   are   designated    as    Rndio   pnclc    sets,   complete 

(year  and  serial  number).    Incomplete  pack  sets  will  not  be  designated 

as  such. 

Units  which  are  complete  are  designated  under  T'nit  headings  given  above. 

Units  which  are  incomplete  are  designated  under  Crfrnponent  fxirt  headings 

given  above. 
The  model,  year,  and  serial  number  will  always  be  shown  in  connection 
with  operating  chests  and  hand  generators.     With  masts  the  type  will 
be  noted. 
Rectitiers.      (All  data  upon  manufacturers  name  iilate  umst  be  given  in  re- 
questing any  parts.) 
liectifiers,  mercury  arc,  G.  E.,  complete  with  transformer. 
Reels : 

Pay-out  (Barrow  type,  with  straps)  — 

Straps,  shoulder,  for. 
Take-up. 
Hand,  for  buzzer  wire — 

Cranks  for,  complete  with  pinions. 


(297) 


16  Signal  Corps  Manual  No.  3.— Chapter  8. 

Relays : 

Pocket,  luU-ohm. 
Standard,  150-ohm. 
Box-sounding,  150-ohm. 
Retardation  coil. 
Ribltons.  typewriter. 
Rings : 

Cable  (see  hangers). 

Bridle,  enameled  (see  p.  71,  this  chai)ter,  for  description)- 
Sizes  §  to  3  inches — 
f-inch. 
li-inch. 
Rockets : 

Sequence. 
Yellow-smoke. 
Rods,  ground   (see  p.  71,  this  chapter)  : 
Terminal,  for  cord,  type  C. 
Type  A,  f-inch  by  5  feet. 
Type  B,  ^-inch  by  6  feet. 
Guy,  f-inch  by  7  feet. 
Rope,  manila  (all  standard  sizes)  : 

Weights,  approximate,  per  coil  of  1,200  feet — 
|-incli  diameter,  24  pounds, 
f-incli  diameter,  31  pounds, 
^-inch  diameter,  9.5  pounds, 
f-inch  diameter,  160  pounds. 
f-inch  diameter,  200  pounds. 
|-inch  diameter,  270  pounds. 
1-inch  diameter,  325  pounds, 
li-inch  diameter,  505  pounds, 
l^-incli  diameter,  725  pounds, 
itulilier.  pure   (cable  splicing). 
Sandpaper,  No.  00  to  No.  4. 
Saws,  crosscut,  carpenter's.  28-inch. 
Screw  anchors.     (See  p.  72,  this  chapter.) 
Screw  drivers : 

S-iucil. 

10-inch, 
Screws : 

Lag,  g  by  4  iiwiu^s  (lor  sivuriiig  brace  to  pole). 

Lag.  -i  l)y  4  iiicbcs  (lor  scon-lug  brace  to  pole). 

Machine,  assorted  slz(>s  and  kinds. 

Wood,  as.sorted  sizes  and  kinds. 
Seats,  pole. 
Sets,  switch-key. 
Shellac,  orange. 
Shells: 

Red. 

Smoke. 

White. 
Shovels : 

L<>ng-lian<lleii. 

Short-handled,  mnnd  jioint. 

(298) 


Technical  Equipment  Issued  by  the  Signal  Corps. — Chaolcr  8.  1  7 


Sliiolils.   expansion. 
Signals,   tiring;: 

BiittiTV   coniiiiamlcr. 
Mortar   pit. 
Sleeves : 

Melntyro,  ntpiuM".  spiicin:.:   (ixiw  size  of  wire)  — 

For  No.  S  wire,  B.  ^  S. 

For  No.  10  wire,  R.  iV;  S. 

For  No.  12  wire,  li.  iV:  8. 

For  No.  14  wire.  P..  .V  S. 
Galvanized  iron,  sitlicin.u  {.civt>  si7.(>  <if  wire)^ 

For  No.  S  wire.  B.  W.  G. 

For  No.  !)  wire.  P..   AV.  G. 

l\»r  No.   IL'  wire.   1'..   W.  G. 

For  No.   14  wire.   IV   W.  G. 
Paper,  splicinjr — 

i  by  3  inciies. 

.'VlO   l»y   3   inciies. 
Lead,  .splieinj:   (.irive  inside  dinmetor  ami  lonsth)  — 

1  inch  inside  dinnietor    (2  pounds  ikm"  foot) 

Ij  inches  in.side  diameter  (2J  pounds  per  foot), 
li  inches  inside  diameter  (3*  pounds  per  foot). 
IJ  inches  inside  diameter   (4  pounds  per  foot). 

2  inches  inside  diameter  (4j  pounds  per  foot). 
2A  inches  inside  diameter  (4.S  pounds  per  foot). 

Slide  rule,  atmosphei-e. 

Solder  (see  p.  71,  this  chapter,  for  description)  : 

Half  and  half. 

Resin  core. 

Wiping. 
Soldering  kits. 

Solderall.  or  Weldall,  tuhc^,  size  No.  2. 
Sounders,  main-line. 
Spectacles,  smoked    (in  ca.se). 
Splicing  materials.     (See  p.  44.  this  chapter.) 
Springs,  hook-retaining. 
Staples : 

Blake,  insulating.  No.  .". 

(lalvanized  iron  (all  standard  sizes:  give  size  required). 
Stearine. 

Steps,  pole,  .lialvanized  iron,   i;  hy  10  inches. 
Strand,   messenger.      (See  Wire.) 
Strajis.  i>ii)e    (give  size  required). 

^-inch    (43  to  the  pound). 

5-inch    (35  to  the  pound). 

A-inch   (27  to  the  pound). 

7-inch    (20  to  the  pound). 

1-inch    (17  to  the  pound). 

l^-inch    (13  to  the  pound). 

1^-inch   (13  to  the  pound). 

2-inch   (.">  to  the  pound). 

3-inch   (5  to  the  pound). 

4G5S1°— 17 20 

(299) 


18  Signal  Corps  Manual  No.  3. — Chapter  8. 

Strips : 

Terminal,  standard  porcelain   (12  pair). 
Support,  messenger :  ■ 

For  iron  poles. 
For  wooden  pole^;. 
Switchboard.      (See  p.  73,  this  chapter.) 
Switchboard,  camp  telephone.     (See  p.  70,  this  chapter.) 
Switches,  knife : 

S.  P.  S.  T.  (give  voltage  and  amperes)  — 

Slate  base,  L'oO-volt,  25  amperes. 
S.  P.  D.  T.  (give  voltage  and  amperes)  — 

Slate  base,  25U-volt,  25  amperes. 
D.  P.  S.  T.   (give  voltage  and  amperes)  — 

Slate  base,  250-volt,  25  amperes. 

D.  P.  D.  T.  (give  voltage  and  amperes)  — 

Slate  base,  250-volt,  25  amperes. 

(Knife  switches  ai"e  furnished  in  any  number  of  poles  and  capac- 
ities  required ;   also,   fuse^l  or   unfused.     In   requesting  switches  or 
repair  parts  for  switches,  state  type  and  whether  back  or  front  con- 
nected. ) 
Switches,  master: 
For  16  targets. 
For  24  targets. 
Tacks,  milonite,  No.  IS,  black,  brown,  drab,  or  red. 
Tags,  cable,  small. 
Tape,  insulating: 

Friction  (adhesive). 
Rubber. 
Telegraph  set : 

Induction,  complete  (1912)  — 
Key,  sending,  complete. 
Box,  battery. 
Coil,  induction. 
Frame,  card. 
Knife  switch. 
Sounders,  polarized. 
Box,  containing,  wood  (t)()X  only). 
Tulcpiu^nes.     (See  p.  78,  this  chapter.) 

Telescopes  (more  complete  description  appears  on  p.  41,  this  chapter)  ; 
Type  A.  Warner  &  Swasey,  18  and  24  power. 
Tyi)eC  Warnei-  <S:  Swasey,  24  and  40  power. 
Type  D.  Sussfeld,  Lorsch  &  Co.,  33,  35,  and  40  power. 
Type  10.  Warner  vV:  Swasey,  IS  power. 
Typ('(!.  Lord  P>ury  type,  24,  30,  and  40  power. 
Terminals : 

(.'arbons  for. 

Cook,  can-top  (fused  and  unfused),  sizes  10  to  52,  pairs — 
10-pair,  fused. 
10-pair,  unfused,  M-4. 
.52-pair,  fused. 
Fuses,  type  A-7,  for. 


(300) 


Technical  Equipment  Issued  by  the  Signal  Corps. — Chapter  8.  19 

Thermometers : 

Acid,  12-incli,  unmounted. 

Mercurial. 
Thimbles,  guy  (state  size  of  strand  for  which  required),  f-iuch. 
Time  interval : 

Apparatus,  motor-driven  (1912). 

Bells,  large. 

Bells,  small. 

Switch  panel. 
Torches,  gasoline,  small. 
Trucks,  lance.     (See  Wagons.) 
Tubes,  porcelain,  uuglazed  (give  size  and  length  desired)  : 

§  inch  b.v  4  inches. 

g  inch  by  10  inches. 

i  inch  by  4  inches. 

i  inch  by  6  inches. 

i  inch  by  10  inches. 

g  inch  by  6  inches. 

f  inch  by  8  inches. 

g  inch  by  12  inches. 
Turpentine. 

Twine,  lacing,  Barbour's,  12-strand. 
Typewriters. 
Vane.  wind. 
Varnish : 

Hard-oil  finish. 

Spar. 
Voltammeter,  portable,  trii)le  range,  Weston,  No.  280,  3-15-150  volts,  3-15-30 

amperes,  with  case. 
Voltmeter : 

Bristol,  r(K'ording. 

Portable,  in  leather  case. 

Portable,  .Tagabi. 

Weston,  model  280. 
Voltmeters : 

5-volt,  Eldredge. 

6-volt. 
Wagons : 

Kit  (quartermaster's  escort).* 

Lance  truck. 

Repair  (spring-instrument  type). 

Signal  Corps  instrument  (quartermaster's  escort).* 

Telegraph  (held  wagon  type).^ 

Telephone  (field  wagon  type).* 
Washers : 

Copper  (all  commercial  sizes;  give  size  required). 

Galvanized  iron,  round  or  square  (all  commercial  sizes;  give  size  of  bolt). 
Waste,  cotton. 

1  Standard   Army  escort  wagon. 

2  Spring  wagon  (ambulance),  instead  of  escort  wagon,  issued  to  the  militia,  when  de- 
sired, at  a  cost  of  .$199.50  each.  Quartermaster's  escort  wagons,  when  required  by  the 
militia,  should  be  entered  on  requisition  for  quartermaster's  supplies. 

(301) 


20  Signal  Corps  Manual  No.  3. — Chapter  8. 

Wntrlios.  wrist,  willi  wristlot. 
Wristlet,  for  wrist  watch. 
Wheels,  spare,  lor  wire  carts. 
Wire  (see  p.  81,  this  chapter)  : 

04  mils  diameter,  copper,  iiisulali'd   (No.   14  1>.  &  S.). 
SI  mils  diameter,  .lialvani/.ed  iron  (No.  14  K.  W.  (J.). 
Twisted  pair,  45  mils  diameter,  copper  clad  (No.  17  1>.  vV  S.). 
Buzzer,  on  carriers.     • 

Counterpoise. 

Field.  11-strand. 
Wire : 

Antenna.  7-strand,  32  mils   (radio). 

Antenna,  7-strand,  64  mils  (radio). 

Copper,  hridle,  51  mils,  ruhher-covered,  single.  No.  10  K.  v^  S. 

Copper,  hard-drawn,  81  mils,  No.  12  B.  &  S. 

Copper  clad,  outside  distrihuting,  twisted  pair.  45  mils.  No.   17  1>.  &  S. 

Galvanized  iron,  144  mils  (320  pounds  per  mile).  No.  .0  B.  W.  (J. 

(Talvanized  iron,  100  mils  (190  potuids  per  mile).  No.  12  B.  W.  U. 
Wire : 

Galvanized  iron,  81  mils  (9(5  pounds  jier  mile).  No.  14  B.  AN'.  G. 

Hou.se.  twisted  iiair,  36  mils,  No.  19  B.  tV;  S. 

Messen,irer  strand — 
§-inch. 
^-inch. 

Pothead.  30  mils.  No.  19  B.  c^  S. 
Wrenches : 

Alligator,  8-inch. 

^lonkey,  8-iiich. 

5  sets. 

Zone  signal  equii)ment,  complete: 

Zone  signal  controller,  2-magazine. 

Zone  signal  outlet. 

Zone  signal  bell,  5-inch,  32-ohm. 

Zone  signal  hell,  2i-inch,  32-ohm. 

Switche.s,  push,  zone  return  signal. 

Lamps,  zone  signal  controller,  Tungslen  lilnmciil    (1()-wall.  (J-lSi). 

l>amps,  zone   signal   outlet,   Tungst«'ii   tilaiiienl    (l(t-watl,   S-17). 

liOX.      MKIAI,.       1  i;i!M  IN  \1,. 

'rcrmiiial  lioxcs  iii'o  sometimes  desii'rd  al  disi  i  iiml  ion  puinls  of  an  under- 
ground cable  system  oi-  ulicrc  it  is  (l(>sired  to  terminate  a  limited  number  of 
cables  without  installing  the  large  distriliuting  frame. 

Wooden  terminal  boxes  are  still  furnished  in  special  instances,  but  the 
latest   standard   terminal   box   is  constructed  of  sheet  metal. 

Tlie  first  metal  terminal  boxes  were  installed  in  connection  with  llie  standard 
lire  conli'ol  system,  <*oast  defenses  of  Che.sapeaUtr  F>ay.  'These  boxes  are  of 
siamped-sieel  conslruciion  and  coiisist  of  two  sejmrate  ])arts.  Ilu^  box  proper 
for  containing  the  terminal  sli-ips  and  cross  connections  and  apron  for  pro- 
tecting the  cable  ])otlieads.  'I'lie  boxes  are  of  the  two-terminal  strip  size  oidy, 
it  being  the  intention  to  install  Iwo  oi-  more  side  by  side  if  a  greater  terminal 
striji  cai)acity  is  reiiuired. 

(.302) 


Technical  Equipment  Issued  by  the  Signal  Corps. — Chapter  8,  21 


Fig.  8-1.— BOX,    METAL,   TERMINAL,   1915   MODEL. 


Part 
No. 


Xame. 


Box,  complete  (give  strip  capacity) . 

Box,  door  for " . . 

Box,  apron  door  for 


Reference 
No. 


TTt 


[-1 

m 


S 


-? 


(yj\        [(7) 


)^i 


^    -"4    •  ^ 
"l    '.4    :A 


tfc^     tfc^ 


•o:^ 


^      Trl 


FRONT  VIEW 


T^-l 


i.^*'A^-^'S^^>'^  ''"l-Ja^^:^.->-]^i>"'^"''^^ 


""  WLS  h 


fc;^-^^. 


SIDt  CROSS  SECTION  SECTION  ON  A-B 

Fig.  8-2.— STRIP.   TERMINAL,    STANDARD. 


(303) 


22  Signal  Corps  Manual  No.  3. — Chapter  8. 

A  new  metal  terminal  box  has  been  designed.  This  terminal  box  is  con- 
structed of  No.  IS-gauge  sheet  steel,  the  box  proper  and  apron  for  housing  pot- 
head  being  combined.  This  box  will  be  furnished  in  three  sizes,  namely,  two- 
strip,  four-strip,  and  eight-strip,  respectively,  and  while  it  is  believed  that  these 
three  sizes  will  meet  the  usual  ueeds  of  the  service,  any  one  of  the  sizes  may  be 
installed  in  combination  with  either  of  the  other  two  sizes. 

The  two-strip  size  may  be  iised  for  either  one  or  two  strips,  holes  being  pro- 
vided for  placing  the  terminal  strip  in  center  of  box  when  the  one-strip  size  is 
desired.    The  principal  features  of  the  new  type  of  box  are  as  follows: 

The  cross  piece  supporting  the  lower  door  at  bottom  may  be  conveniently  re- 
moved and  replaced.  This  is  thought  to  be  very  desirable,  especially  in  the  larger 
sizes,  when  pot  heading  cables  is  in  progress.  The  terminal  box  proper  is  equipped 
with  a  bottom  with  apertures  for  brass  tubes  through  which  the  cables  or  pot 
heads  of  cables  enter  the  main  terminal  box.  It  is  intended  that  these  tubes  shall  be 
closed  by  means  of  sealing  compound,  it  being  necessary  to  place  a  disk  of 
wood  or  other  material  in  tho.se  not  in  use,  before  sealing.  For  those  in  use, 
excess  space  should  be  closed  with  waste  or  oakum  before  pouring  the  com- 
pound. This  feature  is  believed  to  be  very  important,  inasnuich  as  heavy 
leakage  has  previously  occurred  in  terminal  boxes  not  so  equipped,  due  to  the 
warm  air  from  duct  line  entering  the  main  portion  of  terminal  box  and  there 
condensing  when  atmospheric  changes  have  occurred.  Entrances  for  the  house 
wires  have  been  provided  by  means  of  one  slot  in  center  of  top  of  box  of  the 
one  and  two  strip  size  and  two  or  more  in  the  other  two  sizes.  Boxes  will  be 
furnished  with  these  slots  closed  by  means  of  a  small  piece  of  metal  clamped  to 
the  box  with  machine  screws,  it  being  intended  that  those  slots  not  in  use  will 
remain  closed  by  this  means,  and  that  those  in  use  will  be  covered  by  the 
molding  through  which  wires  are  led  to  the  box. 

Figure  8-1  shows  the  one  and  two  strip  size,  the  four  and  the  eight  strip 
size  differing  only  in  the  horizontal  dimension  as  far  as  size  is  concerned. 

Figure  8-2  shows  construction  of  the  Signal  Corps  standard  terminal  strip 
which  is  invariably  used  with  the  metal  terminal  boxes. 

BELI.S,    EXTENSION,    I.OT'I)    UINOING. 

The  extension  bell,  loud  ringing,  is  installed  as  an  extension  to  the  ringer 
(call  bell)  of  a  telei)hone  when  telephone  is  installed  where  noise  interferes 
with  hearing  of  the  telephone  ringer  or  where  it  is  desired  to  hear  a  call 
distant  from  telephone.  The  type  issued  by  the  Signal  Corps  is  weatherproof 
and  is  equipped  with  6-inch  gongs  and  a  2  m.  f.  condenser.  The  condenser 
is  connected  in  series  with  magnet  windings  which  are  wound  to  a  total 
resistance  of  2.500  ohms  (each  magnet  1,2.')0).  These  bells  should  be  con- 
nected in  parallel  with  the  telephone  line  circuit,  the  condenser  preventing  the 
operation  of  signal  at  coimnon  battery  switchboard  should  the  telephone  be 
comiccted  to  such  an  api)aratus.  Figure  S-3  illustrates  tlio  extension  bell,  loud 
ringing.     Small  exttiision  bells  are  furnished  for  indoor  use. 


(804) 


Technical  Equipment  Issued  by  the  Signal  Corps.— Chapter  8.  23 


Fig.  8-3.— BELL,    EXTENSION,    LOUD    RINGING. 


Part 
No. 


Name. 


Base 

Cover 

Gong 

Gong,  cuj)  nut  for 

Permanent  magnei 

Electromagnet 

Adjusting  eccentric,  with  screw. 

Binding  post 

Condenser 


Reference 
No. 


1 

2 

3-3 

4-1 

5 

6-6 


SIGNAL   CAKT. 

For  transportinsr  in  the  field  a  large  assortment  of  signaling  equipment  the 
Signal  Corps  has  recently  designed  and  constructed  a  vehicle  termed  "  Signal 
cax't ".     This  cart  is  arranged  to  be  drawn  by  one  horse  or  mule  and  can  be 
closed  to  protect  contents  from  the  elements.     The  interior  is  equipped  with 
jiartitions  suitalily  arranged  for  separating .  and   holding  rigidly    iti   phice  the 
following  signaling  equipment  which  forms  a  complement : 
2  axes,  hand  lineman. 
S  batteries,  tungsten,  type  A. 
18  bool<s,  field  message. 
•J  buckets,  water,  canvas. 
25  candles,  lantern. 
60  cartridges,  Very,  green. 
60  cartridges.  Very,  red. 
60  cartridges.  Very,  white. 
2  cases,  map. 
16  charges,  carbide. 
4  compasses,  pocket. 


(305) 


24 


Signal  Corps  Manual  No.  3.— Chapter  8. 


4  disks,  cijilicr. 

-<1<)  oiivolKpi's.  iiicss:mc. 

y  eratior.s.  i-ubher. 

4  flashlijihts.  Ever  lieaily. 

6  glasse.s,  field,  type  EE. 

4  lielioiiraplis.  complete. 

4  kits,  flag,  2-foot. 

4  kits,  flag.  4-foot. 

i'  kits,  inspectors,  pocket. 

4  lanterns,  field,  acetylene. 

4  lanterns,  candle,  foNling. 

-4  matches,  wind,  boxes. 

-4  pencils,  lead. 

4  pistols.  Very. 

11'  rockets,  .sequence. 

12  rockets,  yellow  smoke. 

4  spectacles,  smoked,  with  cases. 

Figure  S-4  shows  the  arrangement  ..f  tlu>  signal  cart. 


Fig.  8^.— CART,  SIGNAL. 

CAIV.K. 

For  general  des.-npth.,,   illus,  ra.  ions,   ,„;,„„..,•  ..r  spllHng  and   inslallation   of 

-'I.-,    .-MM.   sysl.MMS    and    ud.l.-s    nC   .„,„     hnes,    .ppn.ve.l    ,yp..s.    ,l,e    .vader    is 

H.M-red    ,.,  (  hapter    1    .,r   ,„is    .nanu.-d.      K.,,-,    ,is,s   .„■   ,,,1    .-nhies    „sed    U,   dale 

should";  '"■'"•""!  '"?'"■"  '•''  =  "•"•"■'-"<-  •"•  "-•>'  'yp.-,  Ihe  (ollowing  tables 
M.  mid  be  ..x..u,n,H.d.  I,  will  1.,.  ,,..,,.1  Ihal  latest  :,ppn,ved  (vpes  are  als.. 
indicated   in   thes,.  |id)les. 


(.-.Odi 


Technical  Equipment  Issued  hy  the  Signal  Corps.     Chapter  8. 


For   <-i)iivciiicii(i'   llic   Siu'iiiil    <'<'i'|is   cMhlfs    iii:iiinrii<lun'(l    Id   ihilc   may   Itf  di- 
vidt'd  iiitn  six  classes,  viz: 

Kul)l)er  insulation.  sul)niariii(',  serial  I.v])c  Nos.  1  to  L'(mi. 

Rubber  insulation,  subterranean,  serial  type  Nos.  201   lo  ,S(H). 

Pajier  insulation,  arnioi-e<l,  serial  type  Nos.  301  to  400. 

I'aper  Insulation,  aerial,  imarniored,  serial  type  Nos.  401   to  ."i(M). 

Special  types,  serial  type  Nos.  HOI  to  000. 

Power  cables,  serial  tyi>e  Nos.  0(»1   lo  Ton. 

Description  of  iiiixs  of  ruhhcr-iuKuUtiion  submarine  cables. 


1 

2 

3 

1 

4 

5 

9 
10 

Desisiwlion. 


9 

^ 

10 

7 

11 

7 

12 

1.3 

i:i 

Hi 

U 

1  -, 

17 
17 

10 

17 

17 

0 

{1899 
1900 
{1889 
1900 
{1899 
1900 

l-conductor,  experimental,  lifiht 190' 

2-conductor 190 

.5-conductor,  1-pair,  3-straight 190 

7-conductor,  2-pair,  S-straight 

9-eonductor,  3-pair,  3-straiKht 

11-conductor,  4-pair,  3-straight 

13-conductor,  3-straight,  5-pair 

17-conductor,  7-pair,  3-straight 

l-conductor 

3-conductor,  San  Francisco 

4-conductor,  New  London 

2-conductor 

l-conductor 


1 

Conductor. 

o  o 

1 

1 

22  . 

g 

T. 

—  i  — 

p. 

IS 

3 

19 

4 

20 

5 

21 

G 

22 

14 

23 

14 

24 

14 

2.3 

14 

2fi 

14 

27 

14 

28 

14 

29 

338 

30 

338 

31 

338 

32 

338 

33 

338 

34 

338 

190 

190 

190 

190 

190: 

1902 

1902 

1902 
1902 
1902 

l-conductor,  Int. ,  Alaskan 1903 

2-conductor,  Int.,  Alaskan 1903 

l-conductor,  rock,  Alaskan 1903 

I 
l-conductor.  shore  end,  Alaskan !  1903 

I 

l-conductor,  deep-sea,  Alaskan '  1903 

F.  C,  Portland,  4-pair '  190:J 

F.  C,  Portland.  4-pair.  and  4-stralght '\  1903 


F.  ("..  Portland.  2-pair.  and  4-straight. 
F.  C.  Portland.  3-pair.  and  3-straight . 
4-pair.  3-straiglit 

4-pair,  4-straight 

2-pair 

l-conductor,  F.  C 

2-pair,  F.  C 

3-pair,  F.C 

4-pair,  F.C 

5-pair,  F.  C 

G-pair,  F.  C 


1903 
1903 
1903 

1903 

1903 
1905 
1905 
1905 
1905 
1905 
1905 


ajS 


28.5 
20.1 
20.1 
20.1 
28.5 


20.1 
28.5 
28.5 
20.1 
28.5 
20.1 
28.5 
20.1 
28.5 
20.1 
28.5 
20.1 
28.5 
20.1 
28.5 

28.5 

28.5 

28. 5 

28.5 

51 

22.0 

51 

22.0 

51 

22.  G 

51 

22. 0 

51 

22.  G 

20.1 

28. 5 

20.1 

2S.5 

20.1 

2.S.  5 

20.1 

28.5 

20.1 

28.5 

20.1 

20.1 

28.5 

20.1 

20.1 

20.1 

20.  1 

20.  1 


In. 


A  } 


81 
81 
162 
162 
102 
91 
51 
182 


182 
204 


2{ 


128 
114 
229 
144 
144 
102 


102 
325 
162 

258 

91 

162 
204 

114 

!ti2 

204 


120 
120 
120 
144 
162 
2(M 
204 


(Continui-il  on  noxt  page.) 


(307t 


26  Signal  Corps  Manual  No.  3. — Chapter  8. 

Description  of  tapes  of  riihher-itisulatloii  suhmarine  rf/6/rs— (_'oiitiiiued. 


35 


no 


40 

334 

41 

33S 

42 

374 

43 

375 

o44 

419 

045 

420 

46 

421 

47 

424 

o.tO 

431 

ool 

431 

a52 

431 

ao3 

431 

a54 

431 

a5,T 

431 

056 

431 

57 

431 

58 

431 

59 

431 

60 

431 

61 

431 

62 

431 

G3 

431 

64 

478 

a66 

4W 

Designation. 


Conductor. 


1-condiu'lor.  deep-sea,  Alaskan 

1-conductor,  Int..  .Vla.skan 

1-conductor,  shore  end.  Ala.skan 

1-conduetor,  deep-.sea.  Pliilipplnes — 

1-conductor.  .shore  end,  Plulippmes . . . 

1-condnctor.  .special,  light 

2-conductor.  F.  C 

3-pair.  special 

3-pair  special 

1-conductor.  intermediate. 

1-condiictor,  deep-sea 

1-conductor 

1-conductor,  Philippines 

1-conductor 

2-conductor 

4-conductor 

(i-conductor 

S-conductor 

10-conductor 

12-condiictor 

1-conductor,  douhle  armor 

2-conductor,  double  armor 

4-condiictor,  double  armor 

0-conductor,  double  armor 

8-conductor,  double  armor 

10-conductor.  double  armor .*. 

12-conductor,  double  armor 

l-conductor.  small 

1-conductor,  .shore  end.  double  armor 


190.J 

1905 

1905 

1905 

1905 

1905 
1905 
1905 

1905 

1906 
1906 
1906 
1906 
1906 
1906 
1906 
1900 
1906 
1906 
1906 

1900 

190G 

1906 

1906 

1900 

1906 

1906 
1907 
1915 


C3  O  *= 


51 

22.  6 

51 

22.6 

51 

22.6 

28.5 

28.5 

20.1 
20.1 

28. 5 

28. 5 

32 
32 
32 
32 

28.5 
28.5 
28.5 
28.5 
28.5 
28.5 
28.5 

28.5 
28. 5 
28.5 
28. 5 
28.5 
28,.-. 

28.  5 
2S.  5 
32 


s 


Jn. 


■h 


A 


102 

/  102 
\  258 
128 
f  128 
\  201 
51 
120 
144 
144 
229 
162 
91 
91,162 
128 
144 
144 
162 
204 
204 
229 
229 
144 
229 
144 
229 
162 
229 
204 
229 
204 
2.S9 . 
229 
289 
229 
289 
51 
162 
263 


"  Inilicates  ajjprovcd  (yi)es  1o  bo  jiurchased  in  the  future. 

Siibmarino  onhlos  for  deep  sen   ;ir(>  usually  <lpliverp(l   in  li'n,L:;tli.s  oT  not  loss 
than  1")  miles. 

The  following  cables  are  usually  furnished  on  i-eels  in  the  t'oilowini;-  leniitlis: 
Types.  20,  80,  41.  f.d,  .".1,  an<l  .vj  in  lengths  of  2  miles. 
Types  .'{1.  82.  .13,  and  ."1  in  Im^llis  of  1   mile. 
Types  88,  84.  ;"»,  ilO.  and  04  In  len.iitiis  of  one-half  iinle. 
Types  ~u   to  08,  ineluslve.  in  siuvial  leiijiths, 
Deei)-sea    sinjrle-conductor   cable,    as    indicated    in    lyjies   8.    1(5.    and   88.   will 
weiLdi  a!)proxinia1cly  .'i.OdO  itouiids  lo  the  mile. 


(S08) 


Technical  Equipment  Issued  by  the  Signal  Corps. — Chapter  8.  27 

The  approximate  weight  of  the  following  rallies  per  statute  mile  is: 

Pounds. 

Type  29 2,  800 

Tvpe  30 10,  000 

Type  31 12.  500 

Type  32 15,  000 

Tvpe  33 21,  000 

Tvpe  34 25,  000 

Type  41___-_ —-^ '- 0.  000 

The  o](l  .MaskuH  cables  weififh  luM-  statute  milo  approximately  as  follows: 

Pounds. 

Type  35 3.  425 

Tvpe  36 5.  450 

Type  37 20.  000 

I)cfirrii>tio)i  of  tiii'cx  of  ruhJtcr-insuhiiiou  fnihtcrrancan  rahlca. 


d 

Z 

a 

o 

03 

^ 

tC 

s, 

H 

m 

201 

202 

203 

204 

20.5 

206 

207 

V2 

208 

12 

209 

12 

210 

12 

211 

13 

212 

13 

I'm 

429 

0214 

429 

021.5 

429 

0210 

429 

a217 

429 

a21S 

429 

0251 

540 

Designation. 


1-pair. 
3-pair . 


5-pair 

6-pair,  and  8-straight . 
5-pair . 


Conductor. 


Q 


1902 
1902 
1902 
1902 
1902 

6-pair,  and  8-straight 1902 

1-pair 1902 

3-pair 1902 

1902 
1902 
1902 
1902 
1900 
1906 
1906 
1906 
1906 
1906 


;-pair 

6-pair 

8-pair,  and  8-straight. 


6-pair . 

8-pair,  and  8-straight 

1-pair 

3-pair 

6-pair 

12-pair 

()-pair .' 

12-pair 

1-pair,  armored,  Greenfield  type. 


p'S 


40 

40 

40 

40 

40 

40 

22.6 

22.6 

22.6 

22.6 

22.6 

22.6 

28.5 

28.5 

28.5 

28.5 

28.5 

28.5 

40 


U   C3 

s 

C3 

5 


Inch. 

A 
■h 
-h 


Inch. 


128 
144 


128 
144 


128 

144 

Steel 

tape. 


"  Indicates  approved  types  to  be  purchased  in  tlie  future. 

These  ruhher-insnlatioii   subterranean   cables  are  furnished  on   reels,   as  fol- 
lows : 

Types  213  and  214  in  one-half  mile  leiifrths. 
Types  2in.  216,  217.  and  218  in  leuirths  of  1.000  feel. 
The  weiirht  of  the  standard  cables  per  statute  mile  is  as  follows: 

Pounds. 

Type  213 ",000 

Type  214 0,  2(X1 

Type  215 H,  100 

Type  216 1-*,  "85 

Type  217 . 18,  800 

T^pe  218 - -«•  000 


(309) 


28 


Signal  Corps  Manual  No.  3. — Chapter  8. 


The  usual  reel  for  the  shipnieiit  of  these  types  of  cable  weighs  400  p(»un(ls, 
has  a  length  of  30  inches,  a  drum  diameter  of  34  inches,  and  sides  5  feet  ti 
inches  high. 

TupcH  of  pu per-inaulution  annorcd  cable. 


Tvpe 
No. 


301 
302 


305 
306 


310 
311 


313 
314 


316 

317 

318 

319 

320 

0321 

322 

0324 

"325 

"326 

"327 


Speci- 
flca- 
tion 
No. 


8 
129 


174 


174 

339 

427 

/  339 

\  427 

/  339 

\427 

(  339 

\  427 

/  339 

\  427 

j  339 

\  427 

/  339 

\427 

f  237 

\427 

/  237 

\427 

/  237 

t  427 

/  237 

\427 

/  237 

;\  427 

/  237 

427 

372 

373 

427 

427 

427 

427 

427 

427 

427 


ppsignation. 


Date. 


10-pair '  1901 

25-pair...- |  1904 

20-pair,  combination 1904 


2.">-pair,  comliination '  1904 


\,     „.  n905 

\.„       .  /1905 

\,.       .  (1905 

'20-pair /{\f^l 

\„.       .  1/1905 

•30-pair te 

.„      .  •  /1905 

'^0-pai'" 1\1908 


5-pair.. 
10-pair. 


/1905 
\1908 
/1905 
\1908 
,,   .  /1905 

l^P^"' ■-•,\1908 

^2->pair ,{i908 

^aopair igs 

bO-pair |i9o^ 

5-pair,  special 1905 

do 1905 

5-pair 1906 

10-pair 1906 

15-pair 1906 

20-pair '  1906 

25-pair I  1906 

30-pair 1906 

oO-paii- '  1906 


Conductor, 

diameter  of 

each  strand 

in  mils. 


Insulation. 


36 '  Double,  paper. 

36 do 

(S-pair,  36 I 

{l2-pair ■ do 

|3-strand,28.5  I 
j  10-pair,  36... 

<  15-pair > do 

l3-strand,28.5  | 

....I do 


|36. 

}».. 

|36.. 
}3.,.. 
}36.. 
I36.. 
|36.. 
}36.. 
|36.. 

}«.. 

36.. 


-do. 
,  .do. 

.do. 
..do. 
..do. 
..do. 
..do. 
..do. 
.  .do. 
.  .do. 
.  .do. 


.\rmor  wire, 

diameter  in 

mils. 


144 
144 


120 

120 
120 
120 
144 
144 
144 
204 


Thick- 
ness of 

lead 
sheath. 


Inch. 


-do. 

.do. 
.do. 
.do. 
.do. 
-do. 
.do. 
.do. 
.do. 
.do. 


J  and  A 
J  and  A 
J  and  A 
1  and  ,^ 
;  and  -h 
;  and  h 


144 
144,204 
204 
204 
204 
229 
229 
229 
229 


"  Indicates  approved  types  to  he  purcha.sed  in  the  future. 

The  armored  paper-insulation  cables  ar(>  su[)pli(Ml  under  (H'rtnin  C(»nditions  for 
submarine  work.     Tiiey  may  also  \)v  used  for  subterraiu>an  work. 
Type  303  weighs  22,()00  pounds  per  stalut*'  mile. 
TyjK'  304  weighs  25,000  poiiinls  ]n'v  slatulc  nillc. 
Types  303  and  304  when  shipix'd  in  mile  IculiIIis  aro  pi-ovidcd  witli  reels  weigh- 
ing ."i,0(M)  pounds,  iiaviiig  a  Jcngl  b  of  7  feci,  a  diameter  of  side  of  S  feet,  and  a 
shaft  ")  inches  iti  diameter  and   Ki  leel   bmg. 

The.se  cables  are  usually  ordered  in  lengths  to  s\nt  the  installation  for  which 
lliey  are  designed,  so  as  to  be  inslalle(|  willioul   splices. 


(310) 


Technical  Equipment   Issued  by  the  Signal  Corps. — Chapter  8.  29 

Types  of  (louhJc  jxijitr-iiisiildtioii,  Icdd-covc red.  iiiKiniiond  cable. 


Type 
No. 


"401 

"402 

"403 

1404 

''40.'> 

"40(1 

"407 

"40S 

"409 

411 

412 

413 

414 

415 

41ti 

417 

41S 

419 


Designation. 


10-pair. 
1.5-pair.. 
20-pair.. 
2.5-pair. . 
30-pair.. 
40-pair.. 
.5()-pair., 
".Vpair. . 
UM»-pair 
10-pair.. 
l.vpair.. 
20-pair.. 
25-pair.. 
3n-pair.. 
40-pair.. 
."iO-pair.. 
7.5-pair.. 
100-pair. 


Con- 
ductor, 
diameter 
of  each 
strand 
in  mils. 


36 

36 

36 

36 

36 

36 

36 

36 

36 

2.1.3 

25. 3 

25. 3 

25. 3 

25. 3 

25.3 

25. 3 

25.3 

25.3 


Thick- 
ness of 

lead 
sheath. 


.Vppro.x- 

imate 
outside 
diameter. 


Inchfs. 
0.  722 
.797 
.872 
.922 
.982 
1. 113 
1.208 
1.443 
l.t)38 
.607 
.682 
.7.37 
.787 
..827 
.943 
1.023 
1.193 
1.353 


Weight 
per  stat- 
ute mile. 


Pounds. 
5,  .370 
6. 193 
7,0.>4 
7, 693 
8,416 
11,083 
12,445 
15, 829 
18, 860 
4, 229 
4,937 
5.  .549 
6.088 
ii,.520 
8,664 
9,  fi46 
11,890 
14, 0.50 


Weight 

per  l,0fKi 

feet  of 

ca1)le 

and  reel. 


1,180 
1.368 
1.55S 
1,700 
l,8t» 
2,448 
2, 7.50 
3,497 
3,967 
935 
1,093 
1,226 
1,345 
1.441 
1.914 
2.131 
2,627 
3,106 


n  Indicates  approved  types  to  be  purchased  in  the  future. 

Tills  cat)!*'  i.s  iisimlly  furnished  on  reels  in  lengths  of  1,000  feet;  length  is 
slated  in  purchiisc  order,  ('able  reels  are  usually  33  inches  in  length,  and 
diameter  from  .IG  to  72  inches. 

Types  of  poirer  cahlcs  i  Siiecifiratinii   'i-ll). 


Type  Nos. 

1 

3 

2 

•3 
g 

a 

o 

ter  of  single  wires- 
mils. 

ance    of   conductor 
1,000  feet,  68°  F. 

—  3 

Length  on 
reel. 

o 
© 

s 
a 

.2 

•V 

2 

.a 

i-i 

hi 

"3    . 
CO 

■^  a 

a> 

<B 

<9 

S^ 

u 

.a 

a 

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1 1ndicates  approved  types  to  be  purchased  for  stock  in  the  future. 

Special  types  of  power  cable  that  have  I)een  purchased  in  the  iiast  for  special 
purposes  are  as  follows : 

Type  No.  G29ff  conforms  to  type  No.  (i2!).  with  the  exception  that  one  wire, 
o9.1  mils  in  diameter,  of  the  condmtor  is  reiilaced  by  a  potential  condu<-tor 
made  up  as  follows :  Conductor  to  consist  of  16  strands  copper  wire,  each  10 


(311) 


30  Signal  Corps  Manual  No.  3. — Chapter  8. 

mils  in  diameter,  having  an  area  of  1,600  circular  mils,  with  a  serving  of  cotton 
and  covered  with  an  even  layer  of  rubber  compound  to  a  uniform  diameter  of 
one-tenth    (ro)   inch,  the  conductor  being  well  centered  in  the  insulation. 

Type  643fl  conforms  to  type  643,  except  that  four  conductors  i02  mils  in 
diameter  are  supplied. 

Type  663tf  conforms  to  type  663.  except  that  four  conductors  102  mils  in 
diameter  are  supplied. 

The  reader. is  referred  to  chapter  4  of  this  manual  for  general  information 
concerning  cable,  its  installation  and  accountability. 

SrBMAJUNE    (ABLE    GEAK    AND    SUPPLIES. 

Anchors,  mushroom,  ordinary.  Supplied  in  sizes  of  1.  2,  2A.  3.  4.  and  ,"> 
hundredweight. 

Anchors,  mushroom,  patent  (Johnson's  patent  removable  shank).  Supplied 
in  sizes  of  1,  2,  24,  3,  4,  and  5  hundredweight. 

Blocks,  wood  or  iron.  Specify  whether  plain  or  snatch  type,  number  of 
sheaves,  and  length  of  block  in  inches. 

Buoys,  automatic  whistling.  Weight.  18  lunuh-edweight ;  safe  load,  2.1  hun- 
dredweight. 

Buoys,  cablp.  Specify  length  and  diameter  or  carrying  capacity  desired,  or 
both.  These  can  be  obtained  in  capacities  from  3  hundredweight  to  6  tons. 
Specify  bridle  chains  for  same  when  desired. 

Boats,  cable   (also  called  cable  cutters). 

Blades  for  hacksaws ;  dozen.     Specify  length. 

Chain,  bridle.  Usually  made  uj)  in  lengths  as  desired  and  fitted  with  egg  links 
at  each  end.  Necessary  to  specify  size  of  links  or  state  breaking  strain.  The 
type  is  usually  crane  chain  and  size  is  the  thickness  of  the  link.  To  obtain 
exact  duplication,  al.so  specify  the  oiitside  width  of  the  link  and  the  pitch, 
which  is  the  distance  between  similar  points  of  successive  links. 

Charts.  Give  serial  number  and  specify  whether  Coast  and  Geodetic  Survey 
or  Hydrographic  Office  edition. 

Chronometers,  marine. 

Clamjis,  buoy  lamp. 

Coats,  oilskin. 

Counters,  revolution. 

Core,  cable,  feet.     For  test-room  connections  and  leads. 

Couplings,  for  chains.  Specify  size  and  kind  of  coupling,  wlietiier  with 
swivel  and  egg  links  or  simply  shackles. 

Crinolines,  cable  tank.  Manufactured  only  according  to  specifications  for 
each  particular  case. 

Cut-meter.  This  is  a  direct-reading  sju'ed  indicator  which  c;in  be  applied  to 
any  moving  surfiice. 

♦  'utters,  cal)h'.  A  ixirtable  bolt  cutter  tluif  may  i)e  nxtunted  on  a  block  with 
b.indles.     It  is  su]iplie(l  for  u.S(!  about  the  decks  of  cable  ships. 

Dividers,  i)ropftrtional. 

Dividers,  steel,  navigator's. 

Dynamometers,  large  size  25  tons  sti-ain.  sninll  size  strains  to  10  tons. 

Frames,  hacksaw.     Adjustable  f\H"nis]ie(l  unless  length  is  st;ited. 

Gauges,  wire. 

Grapnels,  ordinary  H-pntng  laii  be  ol)tained  in  sizes  of  1,  U,  2,  2^,  24  long 
prong,  3,  and  3^  hundredweight. 

(312) 


Technical  Equipment  Issued  by  the  Signal  Corps. — Chapter  8.  31 

Grapnels,  boat,  weight  al^out  23  pounds. 

Grapnels,  Janiies(ni"s  rook,  2  types,  one  having  Hal  prongs  and  tlie  otiier  with 
Itrongs  forked  at  shank.     Type  with  flat  prongs  preferred. 

Grapnels,  Johnson's  renewable  section. 

Spare  prongs  for  same,  short. 

Spare  prongs  for  same.  long. 

Grapnels,  Lucas  patent  cutting  and  holding,  complete,  witii  knives. 

(Jrapnels.  centipede,  can  ])v  (il)taiiu'd  in  sizes  of  X,  li  ^h  2,  2A.  ;{,  and  Si 
hundredweight. 

Grapnels,  centipede,  boat,  weight  30  pounds. 

Grapnels,  Murphy's  patent  centipede,  in  sets  of  6  each,  oonsisiiug  of  -1  grap- 
nels and  2  spare,  and  including  4  shackles.  Can  be  obtained  in  4  sizes,  weights 
per  section  as  follows :  20,  45,  5."),  85  pounds  each. 

Hats,  oilskin. 

Hose,  steam,  flexible  copper,  1?,  and  2  inch  sizes. 

Hose,  steam.  5-pIy  rubber,  l™  and  2  inch  sizes. 

Hose,  .steam,  8-pIy  rubber,  wire-wound,  11  and  2  inch  sizes. 

Hose  couplings.     Re(piisition  for  steam  hose  specify  length  of  sections. 

Hauling-ofC  geai",  steam  or  electric.     For  electric  specify  voltage. 

Ii'ons,  calking,  3  per  set. 

Irons,  soldering,  electric.     Specify  voltage. 

Knives,  cable  sheath. 

l.ami)s,  alcohol. 

Laini)s,  buoy;  can  be  obtained  in  various  sizes.  Ship's  anchor-lights  usually 
supplied.     Specif.v  size. 

Lamp  frames  for  attachment  to  flagstaifs  and  buoy  triixxls. 

Lamp.s,  blow.     (See  "Torches,  blow.") 

Lamps,  incandescent.  Specify  voltage  and  candlepower.  Edison  sockets  will 
be  furnished  unless  otherwise  indicated.  Straight  filament  lamps  are  supplied 
for  testing  room  galvanometers.  Special  lamps  for  telephoto  and  Ardois  must 
have  voltage  and  maker's  name  specified. 

Lanterns,  tin. 

Lead,  red,  pounds.  Supplied  for  preservation  of  cable  gear.  Unmixed  will 
be  supplied  unless  otherwise  specified. 

Leads,  deck,  several  sizes  and  kinds  of  1.  2.  and  3  roller  leads. 

Leads,  heaving,  12  and  28  pound  weights. 

Lead,  sounding,  for  Thompson  machine. 

Leather,  rigging,  sides.     Specify  thickness  and  (piality. 

Logs,  tafliMil,  with  propeller  and  line. 

Liiflvs.     Specify  length,  whlth,  and  size. 

;\Iachines,  cable,  usually  classed  as  "idcU-up."  "'pay-out,"  or  combined 
••  picking-up  and  paying-out."     To  be  accounted  for  by  name  of  maker 

-Machines,  1).  S.,  sounding,  Sig.sbee. 

Machines,  electric,  vulcanizing.     Specify  voltage. 

Mallets,  calking. 

Mallets,  serving,  wood. 

Mallets,  serving,  iron. 

Mushrooms.     (See  "Anchor,  mushroom.") 

Marline,  spikes. 

Needles,  sail,  dozen. 

Oil,  boiled  linseed,  gallons. 

Oil,  engine,  barrels. 

Oil,  cylinder,  barrels. 

(313) 


32  Signal  Corps  Manual  No.  3. — Chapter  8. 

Padlocks.  Specify  make  desired  and  size.  Usually  unsatisfactory  when  fur- 
nished assorted. 

Paint.     Specify  whether  mixed  or  unmixed. 

Palm.s,  sailor's  sewing. 

Rope,  grapnel,  combined  wire  and  manila,  breaking  strain  lo  tons ;  weight 
per  thousand  fathoms,  exclusive  of  httings.  5o4  hundredweight. 

Rope,  gi-apnel  and  buoy,  combined  wire  and  manila,  breaking  strain  13i  tons; 
weight  per  thousand  fathoms,  exelusive  of  fittings.  49*  hundredweight. 

Rope,  buoy,  combined  wire  and  manila,  breaking  strain  7A  tons;  weight  per 
thousand  fathoms,  exclusive  of  httings.  24  hundi-edweiglit.  Specify  the  length 
of  sections  of  grapnel  and  buoy  ropes;  also  that  each  length  l)e  equipped  with 
proper  fittings. 

Rope,  manila,  coils.  Specify  .size,  inches  (cireumference).  Rope  s\ipi»liiMl  only 
in  units  of  coil.s.  Number  of  feet  in  a  roW  not  tixed.  Three-strand  will  be  sup- 
plied unless  4-strand  is  specitied. 

Rotometers,  Elliot  (I'evolution  counters). 

Scales  for  T.-B.  sounding  tubes. 

Sextant. 

Shackles.  Specify  size  whether  screw  or  pin;  givc^  s\zo  and  also  length  and 
width,  as  some  types  are  unsuitalde  for  u.se  with  grapnel  rope. 

Sheaves.  There  is  such  a  great  variety  of  sizes  and  kinds  that  recpiisitions 
should  clearly  specify  type  and  dimensions. 

Si)un  yarn.  3  yarn. 

Shots,  .sounding.  Can  be  obtained  in  weights  from  40  to  00  pounds.  Should 
be  purcha.sed  by  cable  ship,  as  required. 

Splicing  tool.     A  disk  with  handles  for  laying  on  armor  wire. 

Swivels.  Can  be  obtained  in  various  sizes  and  with  various  sliaiied  liidcs 
attached. 

Slip-hooks  (detaching  hooks).  Has  trigger  for  releasing  buoys.  Three  sizes — 
small,  medium,  and  large. 

Tubes,  glass,  sounding,  for  Thompson  machine,  10  tubes  per  case. 

Tubes,  sounding,  Tanner-Blish,  for  Thompson  machine,  frosted  glass. 

Tube,  brass,  sounding.  To  attach  to  sounding  wire  and  contains  the  glass 
tube. 

Tube  boxes  for  T.-B.  sounding  tubes. 

Tags,  cable,  linen. 

Telegraphs,  special.  Refers  to  pedestal  dials  completp ;  also  known  as  "  shij)'s 
telegraph."  !{(>(piisitions  for  chain  or  i)ulleys  specify  exact  size,  and  for  the 
telegrajilis   fui'nisii   a   sketch   showing   liic   lettering  desiri'd   for   the  dial. 

■■i'cleiilioto  outfits   (Ardois).     To  bo  accounted  for  by  luiniiier. 

'J'hermometers,  deei)-sea  sounding.  These  thermometers  on  being  revci-scd 
when  heaving  in  indicate  the  b()ttom  lemiKM-ature.  Negretti  iV  Zaniltra  t,\pc  will 
be  stipplied  unless  otherwi.se  indicated. 

'riicniioiiictcr  cases.  For  reversing  I  licnnonielcr  to  obtain  bottom  lenipera- 
(ure. 

Tliiinldcs.  Can  he  sui)pli('d  in  great  variety  of  sizes  and  shapes,  (ialvanized 
iron   will  be  sup|)lied   uidess  othci'wisc  specified. 

Torc-hes,  blow.     (Jasoiinc  type  will   he   rurnished   unless  otherwise  siiecifi(>d. 

Trays,  vulcanizing.  These  are  for  melting  parallin  for  vtdcanizing  Joints. 
<'an  not  be  purchased  in  open  market.  When  new  one  is  re(|uired.  old  one 
sliouhl  he  furnished  as  a  sample  (o  maiiufaclurer. 

Waste,  cotton,  bales,  about   100  pounds  per  bale. 


CMi) 


Technical  Equipment  Issued  by  the  Signal  Corps. — Chapter  8.  33 

Wiro,  seiziii.LT.  This  is  :i  sofi  (!.  1.  wire,  -to  mils  in  ilijiiiicln-,  for  serving;  aniior 
of  1>.  S.  t-altlc. 

Wire,  soundinf?,  T-stnuHl.  fm-  Thoniiison  luui'hiiif.  Su])i(lic<l  in  U-nKths  of  300 
fathoms. 

Wiiv,  deep-sea,  .soundinj;,  fathoms.  This  is  "No.  11  music  wire,"  approxi- 
mately 28.5  mils  in  diameter,  breaking  strain  about  207  pounds.  Supplied  in 
sealed  tin  cans  containing  1,000  fathoms  of  wire. 

Hooks  supiilied  on  cable  testing  and  engineering:  Deep-Sea  Explorations 
(Fish  Commission  edition).  Ehvtrical  Engineer's  INx-ket  Book  (Foster),  Elec- 
trical Testing  for  Telegraph  Engineers  (Young),  Submarine  ('able  I^aying  and 
Kepairing  (Wilkinson),  Submarine  Telegraphs  (P>right),  Submarine  (.'able 
Testing   (Fisher  v^  Darby).  Electrical  Testing   (Kent). 

WIKK     C.VUT. 

Carts,  wire,  type  L,  comph'te  (Ihe  type  I>  wire  cart,  when  furnished  com- 
I)lete,  is  sui)plie(l  with  the  following  extra  parts:  1  wheel,  except  in  the 
case  of  Signal  Corps  tield  companies  of  the  Regular  Army,  which  are  sup- 
plied only  with  the  number  authorized  by  existing  orders;  1  paulin ;  1  axle: 
1'  brake  bands;  bearings  for  1  reel,  complete;  1  crank,  reel;  1  wrench,  axle: 
1  can,  oil,  steel,  pint  size;  and  1  canvas  roll  containing  the  following  tools: 
1  chisel,  cold,  6-inch ;  1  screw  driver,  5-inch ;  1  screws  driver,  10-inch ;  1  ham- 
mer, claw.  Hi  ounces;  1  wrench,  monkey,  8-inch ;  1  pliers,  side  cutting,  8-inch ; 
1  wrench  set,  S,  to  fit  special  bolts  on  carts;  1  wrench,  alligator,  S-inch)  : 
Maintenance  parts — 

Axle,  with  nuts  and  pins. 

Band,  brake,  complete. 

Bearing,  roller,  for  driving  gear. 

Bearings,  roller,  for  reel. 

Block,  terminal. 

Bolt  and  nut,  7A  by  |,  for  doubletree,  with  cotter-pin  hole  drilled  in 

same. 
Bolt  and  nut,  for  tire,  3  by   is. 
Bolt— 

For  axle  bracket,  7*  by  |,  slotted-head  castle  nut. 
For  center  axle  bracket,  4*  by  §,  slotted  head  castle  nut. 
For  countershaft  hanger,  7*  by  i,  slotteil-head  castle  nut. 
Bolts,  for  wheel  hub. 
Bolt,  hanger,  pole  prop. 
Box- 
Center  axle. 
Outer  axle. 
Bracket— 

For  pole  prop. 
Plunger. 

Kod,  reel  guide,  center  or  side. 
Brake,   reel,  with  raybestos — 
Right. 
Left. 
Biishing  and   luit,  for  doubletree. 
Bushing,  tiber,  for  reel. 
Can,  oil — 

10-inch,  bent  spout,  copper. 
Steel,  pint  size. 
46581°- 17 21  (315) 


34  Signal  Corps  Manual  No.  3. — Chapter  8. 

Carts,  wire,  type  L,  complete — Continued. 
Maintenance  parts — Continued. 
Cap- 
Hub. 

Roller,    antifriction. 
Chain  and  ring,  for  doubletree. 
Chain,  pole  prop. 
Clevis,  for  commercial  reel  shaft. 
Clutch,  complete,  with  gear    (33  teeth). 
Conductor,  terminal  block. 
Connector — 

Ground,  for  wheel    (on  spoke). 

Inside. 

Outside. 
Cotter  pins — 

For  axle. 

For  bolt,  for  axle  bracket. 
Crab,  pole. 
Doubletree. 

Eye,  conductor,  ternnnal  block. 
Gear — 

Countershaft,  with  shaft  attached    (09  teeth). 
•  Driving    (66   teeth). 

Reel   (30  teeth). 
Handle,  crank. 

Holdback,  for  pole  neck  yoke. 
Hub,  wheel. 
Insulator — 

Block,  for  inner  part  of  reel. 

Block,  for  plunger  bracket. 

For  singletrci". 

Washer,  on  plunger  bracket. 
Lever — 

Brake,  foot. 

Clutch. 

Reel  brake,  foot. 
Nut,  axle — 

Left. 

Right. 

riiuiiii. 

Tin  and  ciiaiii.  split,  for  conHucrcial  reel  shaft. 
Pin,  connecting,  for  foot  lever. 
Pins,  pivot — 

Foot  lever. 

Reel  brake. 
I'lunger. 

I'olf.  coiiiplctc',  including  pule  pi'op  and  bracket. 
Pole   (wood  only). 
Prop,  pole. 

Raybcstos,  facings,  for  iccl  liraUc. 
Keel,  complete,  without  roller  bearing. 
Ring,  contact,  for  reel. 


(316) 


Technical  Equipment  Issued  by  the  Signal  Corps. — Chapter  8.  35 

Carts,  wire,  type  L,  complete — Continued. 
Maintenance  parts — Continued. 
Rod— 

Clutcli  connecting. 
Connecting,  brake  lever. 
Reel  guide. 
Roller,  antifriction. 

Bearing  for. 
Roll,  ltK>l.  canvas,  complete,  with  tools. 
Case,  canvas. 
Chisel,  cold,  6-inch. 
Hammer,  claw,  11^  ounces. 
Pliers,  side  cutting,  8-inch. 
Screw  driver — 
5-inch. 
10-inch. 
Wrench — 

Alligator.  8-inch. 
Monkey,  8-inch. 

Set,  S,  to  fit  special  bolts  on  carts. 
Screw — 

For  contact  ring   (R.  H.  machine.  2-inch,  20-thread,  No.  14),  per 

gross. 
Set,  and  lock  nut.  for  center  axle  box. 
Screws  for  reel  gear. 
Shaft  reel,  commercial. 
Shaft  rock- 
Brake  lever. 
Clutch. 
Singletree. 
Spring,  plunger. 
Washer,  fiber,  for  reel. 
Wheel,  complete. 
Wrench,  axle. 
Yoke- 
Axle,  with  brake-band  hanger. 
Neck. 


Figures  8-5,  S-6,  8-7,  8-8  illustrate  cords  used  with  various  apparatus  sup- 
plied by  the  Signal  Corps.  Figure  8-9  illustrates  terminals  used  In  connection 
with  the  cords.  The  number  sho\\'n  for  each  cord  is  the  latest  number  adopteil 
and  should  be  used  in  referring  to  tlie  cords. 


(317) 


3() 


Signal  Corps  Manual  No.  3. — Chapter  8. 


(318) 


Technicai  Equipment  Issued  by  the  Signal  Corps. — Chapter  8. 


(319) 


38 


Signal  Corps  Manual  No.  3.— Chapter  8. 


3  4 
2 

V 

4 

\ 

(320) 


Technical  Equipment  Issued  by  the  Signal  Corps. — Chapter  8.  39 


(321) 


40  Signal  Corps  Manual  No.  3. — Chapter  8. 

Made,  cfnickd plai&d  brass  orgcrman  silver,  except  where,  shown  oUicrwise. 


■jS 


I'     ^'  t    ls-^_ 


T 


H^Qc 


.(Glazed  cotton 


•No  21(028') 5ta:hYire 

2 


"^  ^ 


.  Condudur  looped 

4 


S 


/]j  Conductor  wrapped 
g1  wi/7  //he  coppcj-  yrirc 


•-t-^5  .TSl  3j~^^-  h 

-J*]    |»    Na26(.OI6)    -M  VHa44^0m')drill   p]       No  22 (.025') 


7a 


8 


,    \nrappca  nith 
*~4r\  fineooppcrnire. 

6 


^tfi— l^^B 


»    I.   Z"J 


nj~i^^ 


'513^ 


14  ^^^        16 

Fig.  8-9.— CORDS,   STANDARD,  TERMINALS    FOR. 


Following'  i.s  ii  liiift'  (lt>sci-iplL(in  t)l'  Held  t,'lassos  and  telcscojios  Is.sued  by  the 
Si;;iial  Cnrps, 

FIELD   Ca-ARSER. 

T\ipc  .1  "  i!)iO". — !\Iafrnlflcntlon  npproximately  .'VJ  and  Hi  dlamoterR;  rialiloaii 
lypc;  ohjcct  icii.s.  H  inches;  luterpupillary  adjustment;  (an  heather  llnlnli ;  tan 
leallier  carryin;:  case  witli  c<)nii»ass;  weight  of  Khiss  eoiiiitU^te  with  case,  cord, 
and  straj).  '2H  ounces.  At  a  distance  of  l.(MM)  yards  th»'  Meld  of  view  has  a  diam- 
eter of  110  yards  for  the  .3i-iH)wer  and  70  yards  foi'  llie  r>i-i)ower.  Leni;tli  of 
jrlass  closed.  4  inclie.s.  This  j^lass  is  issue<!  as  a  i)art  of  tlu>  vlsmd  slfi'ualln^i'  kit 
to  comparncs  ol'  Coast  Artillery,  Infantry,  and  I'liilippine  Scouts,  and  fo  t  i-oops 
of  Cavalry.     I'rice.  .$14.0".. 

7'///K'  //.— MaKnitic;ilion  :ippio\iiiialfly  4i  and  0.\  diameters;  (Jalilean  tyjie ; 
object  lens,  1.?  inches;  iiitcrpnpillai-y  adjustment  ;  tan  leather  tinisli  ;  tan  leather 
earryinj;  ease,  willi  comjiass;  weiL'lit  of  ^dass,  com|ilete  with  case,  cord,  and 
strap,  .'*1  ounces;  len;,dli  of  ,i,dass  closed.  4}  inches.     .\l  a  ilistance  of  1,000  yjirds 


(322) 


Technical  Equipment  Issued  by  the  Signal  Corps. — Chapter  8.  41 

the  licld  nl'  view  lias  a  diameter  of  100  yards  fur  the  4^-povver  and  70  yards 
for  llu'  (J^iMiwer.  This  irhiss  was  foniicrly  issued  as  a  part  of  llic  lii-c-cnni  rol 
equil)Uieiil    lo   i'"icld   Ai-|  illci-y.     I'l-icc,  .$17. .10. 

Type  V. — A  liigh-jyower  i)risnialic  l)iiio(uhir,  the  present  issue  heinji  IheTerlux 
10-power ;  object  lens,  1,  inches;  interpui)illary  adjustment;  common  focus  lor 
both  barrels,  and  one  barrel  ecpiipijed  with  indeijendent  focusinji  device;  tan 
leather  Ihiish ;  sunshade;  tan  leather  carrying  case;  weight  of  gla.ss  complete 
with  case,  cord,  and  strap,  48  ounces ;  length  of  glass  closed,  7|  inches.  At  a 
distance  of  1,000  yards  the  field  of  view  has  a  diameter  of  70  yards.  One  glass 
is  issued  to  the  commanding  officer  of  each  machine-gun  company  and  machine- 
gun  troop.    Price,  $39.90. 

Type  D. — Prismatic  binocular,  the  present  issue  being  the  Busch  8-po\ver 
"  Stellux  ;"  object  lens,  f  inch;  interpui)illary  adjustment;  conunon  focus  for 
both  barrels,  and  one  barrel  equlpiied  with  independent  focusing  device;  tan 
leather  finish;  tan  leather  carrying  case;  weight  of  glass  complete,  with  case, 
cord,  and  strap,  21  ounces ;  length  of  glass  closed,  3/e  inches.  At  a  distance  of 
1,000  yards  the  field  of  view  has  a  diameter  of  96  yards.  This  glass  is  issued  to 
field  companies  of  tlie  Signal  Corps,  and,  on  account  of  its  excellence,  light 
weight,  and  small  size  is  especially  suitable  for  the  personal  field  glass  of  an 
officer  who  desires  a  high-power  field  glass.    Price,  $25.10. 

Type  EE. — Prismatic  binocular,  6-power ;  object  lens,  It^  inches ;  interpupil- 
lary  adjustment ;  each  barrel  equipped  with  an  indeijendent  focusing  device ;  one 
barrel  equipped  with  a  mil  scale ;  tan  leather  finish ;  sunshade ;  tan  leather 
carrying  case  with  compass ;  weight  of  glass  complete,  with  case,  cord,  and 
strap,  41  ounces.  Length  of  glass  closed,  4ii  inclies.  At  a  distance  of  1,000 
yards  the  field  of  view  has  a  diameter  of  140  yards.  This  glass  is  the  approved 
glass  for  issue  to  Field  Artillery  organizations.    Price,  $33.75. 

Officers  in  continental  United  States,  Porto  Rico,  or  Ci.ba  making  application 
for  the  purchase  of  field  glasses  should  address  such  aiiplication  to  the  Chief 
Signal  Officer  of  the  Ai*my.  Officers  in  the  Philippine  Islands  or  China  should 
address  applications  to  the  Dei):irtnient  Signal  Officer,  PhiliiDpine  Department. 

The  Government  does  not  pay  transportation  charges  on  articles  sold  to 
officers.  All  applications  to  the  Chief  Signal  Officer  of  the  Army  should  be 
accompanied  by  post-office  money  order  drawn  on  Washington  post-office  or  New' 
York  exchange  for  the  amount,  payable  to  "  Disbursing  officer.  Signal  Corps, 
United  States  Army."  Signal  Corps  form  No.  240,  in  duplicate,  should  accom- 
pany all  applications. 

Unless  otherwise  specified,  field  glasses  will  be  shipped  express  charges  collect, 
the  amount  of  expi-essage  being  deitendent  on  distance  glasses  are  shiiiped.  If 
Insured  parcel-i)ost  shipnient  is  desired,  the  amount  necessary  for  parcel  postage 
should  be  inclu<led  in  remittance.  Shii)ments  of  field  glasses  to  points  in  conti- 
nental United  States,  Porto  Uico,  and  Cuba  are  made  from  Fort  Wood,  N.  Y., 
and  to  points  In  (Mdna  and  the  PhlUiiplne  Islands  from  Manila,  P.  I.  For  rates 
relative  to  insured  parcel  post,  see  Signal  Corps  Manual  No.  7,  revised  edition. 

TELESCOPES. 

Type  A. — Warner  &  Swasoy,  poro-prism.  complete  with  two  eyepieces,  powers 
18  and  24,  with  alt-aziinutli  mounting,  folding  tripod,  and  carrying  case. 

Type  C. — Warner  iV:  Swasey,  tei-restrial,  2-incli  prism,  two  eyeiiieces,  24  and 
40  power,  complete  with  alt-azimuth  mounting,  folding  tripod,  and  carrying  case. 

Type  D. — Sussfeld,  Lorsch  &  Co.,  Galilean,  33,  35,  40  iwwer,  leather  covered. 
with  leather  caps  and  strap,  six  sections,  objective,  2-inch  :  length  closed,  9* 
inches:  open,  37  inches;  weight,  2  pounds  4  ounces. 

(32.'?  J 


42 


Signal  Corps  Manual  No.  3. — Chapter  8. 


Tyi)C  E-1S.T. — Warner  &  Swasey.  18  power,  prisni.itic  (now  desijinated  Artil- 
lery type),  in  black  leather  carrying  case,  with  heavy  wooden  noiifolding  tripod 
(.5  feet  2  inches),  one  eyepiece;  enameled;  objective,  Ife  inches;  length  closed, 
12i  inches ;  open,  13i  inches ;  weight,  telescope,  5  pounds  8  ounces ;  leather  case, 
1  pound  8  ounces :  tripod.  8  pounds. 

Type  G  2-'^  SO.  .'lO.r. — Lord  Bury  type,  one  eyepiece,  5  sections,  black  leather 
covei-ed.  with  leather  caps  and  strap,  without  tripcnl ;  gun  metal.  Oblective,  15 
inches;  length  closed.  10*  inches;  open,  33  inches;  weight.  2  itounds  ;\  ounces; 
tripod,  S  pounds. 

FUSES. 

The  standard  fuses  furnished  by  the  Signal  Corps  in  connection  with  fire 
control  and  post  telephone  systems  are  illustrated  in  figure  8-10. 

With  post  telephone  switchboards,  iiiicn  fuses  similar  to  type  8  are  used  to 
protect  lines  and  cord  circuits.  In  some  instances  the  dimensions  of  these 
fuses  do  not  correspond  with  those  of  any  of  the  standard  Signal  Corps  types 
shown  in  figure  8-10.  This  is  due  to  manufacturers  having  furnished  their 
standard  fuse  mountings  with  the  switchboard. 


4 


K 


TYPES  I  &2 


I 


TJIT— 

TYPES  3&4 

Types  /  and  2  are  special, 
3, 4, 5  and  6  art  National 
EICC  Code,  Standard. 


-  -2-H 

K-i"- 

« 

W  U.  STYLE,  TELE.GRAPH 
TYPE  7 


Amperes  arc  Natl.  Dec.  Code  rating 

TYPE 

AMPS 

A- 

B 

C 

D 

E 

F 

G 

S  C     1 

3-15 

\k 

32 

% 

-       2 

3-15 

\i 

^ 

-       3 

0-30 

2 

%> 

2 

..       4 

35-60 

3 

{1 

^ 

•■        5 

65-100 

A 

Ire 

5i 

i 

i 

■■       6 

110-200 

A\ 

\% 

7^ 

\i 

I 

TYPES  5&6 
I    AMP  ER  E  M  1  CA   Terminals  are^  copper 


POSTAL  5TYLE.  TELLEPHONE. 
TYPE  8 


Z-LINK  FOR.  MASON  ARR. 
TYPE   9 


Fig.  8-10.— FUSES,    STANDARD   TYPES. 


Those  rendering  re(|uisi1ions  U>r  fuses  should  specify  Ihe  Signal  Corps  type 
and  the  ampere  caiJacity  unless  the  fu.ses  desired  do  iiol  correspond  with  any 
of  the  types.  In  the  event  of  the  fuse  not  being  standanl  Signal  Corps -issue, 
the  api)aratus  wilh  which  it  is  to  be  used,  name  of  manufacturer,  and,  if 
I)racticMbl<',  a  sample  of  fuse  slidiild  lie  furnished. 

(■^24) 


Technical  Equipment  Issued  by  the  Signal  Corps. — Chapter  8.  43 


IKON    CONDUIT. 

Loricated  iron  conduit  of  various  sizes  is  furnislied  wliere  extra  protection 
for  plain  lead-covered  cable  or  rul)l>er-covered  wire  is  desired. 

FIBER    CONDUIT. 

Thi.s  is  the  standard  conduit  furnished  for  underground  construction  and  is 
usually  supplied  in  o-foot  lengths,  8  inches  inside  diameter,  with  ends  formed 
for  socket  joint.  Various  size.s  can  be  furnished,  and  conduit  with  screw 
socket  joints  instead  of  ordinary  socket  joints  will  be  furnished  if  satisfactory 
reason  be  given. 

KEY,    STRAP. 

The  standard  strap  key  of  the  Signal  Corps  is  made  in  two  sizes.  They  are 
designated  "  key,  strap,  large  "  and  "  key,  strap,  small."  The  large  strap  key 
has  a  slate  base  .5f  by  3^  inches,  and  the  small  strap  key  has  a  slate  base  4  by  2 
inches.  The  principal  metal  parts  of  the  two  keys  differ  correspondingly 
in  size. 

The  upper,  lower,  and  two  central  contacts  are  of  platinum  wire  40  mils 
diameter,  the  upper  contact  being  adjustable.  Three  substantial  l)inding  posts 
to  which  are  connected  the  external  circuits  connect  with  the  upper,  lower,  and 
central  contacts,  respectively.  Referring  to  figure  8-11,  it  will  be  noted  that 
normally  the  upper  contact  and  one  of  the  central  contacts  are  in  electrical 
contact,  and  that  when  the  straji  is  depressed  by  means  of  the  hard-rubber 
handle,  this  contact  is  broken  and  the  other  central  contact  and  lower  contact 
are  brought  in  electrical  contact.  When  the  handle  is  released  the  ".spring 
brass  "  strap  restores  the  contacts  to  normal  position.  The  two  central  con- 
tacts are  not  insulated  from  each  other. 


Fig.  8-n.— KEY,   STRAP,    LARGE. 


Part 
No. 


Name. 


Reference 
Xo. 


Base,  slate,  complete 

Yoke,  complete 

Yoke,  screws  for  fastening 

Strap 

Strap,  hard-rubber  handle  for 

Contact  screw,  upper ,  complete 

Contact  screw,  upper,  lockmg  nut  for. 

Binding  post ,  complete 

Binding  post,  nut  for 

Binding  post ,  washer  for , 

Contact,  lower,  complete 


(325) 


44  Signal  Corps  Manual  No.  3.— Chapter  8. 

INSLTLATING    AND    SPLICING    MATERIALS. 

[This  list  includes  both   fire-control   aud   general-service  supplies.      Ceneral   specification 
No.  569  covers  insulating  and  splicing  material.] 

A1co1k)1   (jrrain.  wood,  or  denatured)  per  .gallon,  as  ordered. 

Armalac.  per  gallon. 

Asbestos,  as  ordered. 

Asphaltum  varnish,  per  gallon. 

Bandages,  cotton,  rolls  2  inches  wide  by  3  yards  long. 

Beeswax,  yellow,  per  pound. 

Compound,  Chatterton's,  per  pound. 

Cloths,  wiping,  Moleskin,  3,  5,  and  6  inches  square. 

Cloth,  Crocus,  per  quire. 

Cotton,  strips,  i-inch  wide,  in  rolls  5  inches  in  diameter. 

Cotton  wicking,  per  ball. 

Instrument  lacquer,  blue,  colorless,  or  yellow,  per  bottle. 

Insulatine,  per  pound,  in  1-pound  sticks. 

Muslin,  strong,  unbleached,  2  inches  wide,  10-yard  rolls. 

Ozite,  per  gallon,  in  1-gallon  tin  cans.     No.  1  or  No.  2  grade. 

Paraffin,  per  pound,  flat  cakes,  melting  point  not  lower  than  120°  F. 

Paraffin  oil,  per  quart. 

P.  &  B.  paint.  No.  2,  1-gallon  cans. 

Pasters,  gummed,  paper  for  wiped  joints,  2  inches  wide,  11  or  15  inches  long, 
sanitary,  per  hundred. 

Rubber,  pure,  cut  sheet,  on  cambric ;  thickness  of  rul)])er  aliout  0.0235  inch,  per 
pound. 

Rubber,  pink,  60  per  cent  pure  Para,  cut  sheet,  on  cambric ;  thickness  of  rubber 
about  0.012  inch,  per  pound. 

Rubber  cement,  in  pint  aud  half  pint  cans  as  ordered,  specification  para- 
graph 2   (a). 

Shellac  varnish,  orange  or  white,  quarts  and  gallons ;  higli  grades  only. 

Shellac  gum,  orange,  per  pound. 

Sandpaper,  per  quire  or  dozen  sheets,  Nos.  0,  1,  and  2. 

Sleeves,  paper,  i  or  i^  by  3  inches,  per  100, 

Sleeves,  lead,  1,  Ih  2,  2J,  or  3  inches  diameter,  16-inch  pieces  or  In  feet,  "  O  " 
weight. 

Sleeves,  Mclntyre,  give  size  of  wire  in  mils. 

Soft  rubber  tubing.  tV,  ^,  and  J-lncli  bore,  per  foot. 

Solder,  i-osin  core,  H-pound  spools,  per  pound. 

Solder,  liiUf  and  half,  in  l)ars,  i)er  i)oun(i  (.W  parts  tin,  50  parts  lead). 

Solder,  i)liiml)ei-'s  wiping,  in  Ingots,  per  pound  (40  i)ar1s  tin,  (!0  parts  lend), 

Stearine.  in  :l-pound  metal  cans. 

Tape,  friction,  f  inch  wide,  ^-pound  rolls,  per  pound.  In  tin  boxes. 

'rape,  okonite,  J-i)ound  rolls,  per  pound,  in  pastel)oard  l)(»xes. 

'I'wiiic,  lacing,  1-pound  l)alls,  Bai'bour's  "Open  Hand"  brand,  12  strand. 

INSl   1,AIIN(;    COMI'orNDS. 

Tn  f)rder  that  confusion  may  l)e  avoide<l  concerning  (he  use  of  tlie  various 
insulating  compounds  wliicli  are  ordered,  tlie  following  should  be  noted  : 

'I'lie  c(»mpounds  supplied  are:  (Miallerton's  comitound  (first  (piality),  in- 
sulatine, gyite,  ozite,  jiarallin. 

(326) 


Technical  Equipment  Issued  by  the  Signal  Corps. — Chapter  8.  45 

ClHiltcrl())i'ft  cnvi pound. — Chatterton's  coinpnuiid  is  ;i  liij^li-class  insulator  fost- 
in,u  $1  per  pound  and  slioidd  be  used  only  in  scalin;^  ends  of  cable  wliere  they 
are  exposed  to  storage-battery  fumes  or  in  similar  work  wtiere  a  liigh-quality 
insulator  is  required. 

Tnsulntinr. — Insulatine  is  not  a  liigli-quality  insulator,  and  it  is  intended  for 
use  in  sealing  outlet  boxes  where  a  wall  of  rubl)er  exists  between  the  insulatine 
and  the  conductor.  It  should  never  be  used  for  insulating  purposes  only,  and 
is  depended  on  more  for  its  sealing  qualities  than  for  insulation.  Tiiis  material 
is  comparatively  cheap,  costing  about  12  cents  per  pound. 

Gyite. — Is  a  better  grade  than  insulatine,  but  not  as  good  as  ozite. 

Ozitc. — Ozite  is  used  for  sealing  potheads  in  paper  cable  work.  It  may  also 
be  used  for  sealing  the  ends  of  rubber  cable. 

No.  1  ozite  is  hard.  No.  2  is  medium  soft,  and  No.  3  is  soft,  at  approximately 
60°  F.  In  ordering  state  the  purpose  for  whicli  the  material  is  d(>sired  and  the 
conditions  as  to  temperature. 

Paraffin. — Paratfln  is  intended  for  use  in  boiling  out  splices  in  paper  insula- 
tion cable  and  in  drying  tlie  ends.  It  should  never  be  used  in  pothead  work  or 
for  sealing  purposes. 

LINK   (ONSTIUrCTION    MATKRIALS. 

I'riiis  lisl   inchul.'s  both  tire-control  and  ironcTal-scrvico  supplies.] 

Anchors,  guy,  D.  &  T.,  S-incli. 

Anchors,  star,  Ig-inch,  No.   10. 

Anchors,  star,  §-inch,  composition. 

Anchors,  expansion,  i-inch,  composition. 

Anchors,  guy,  Matthews,  6-inch  or  S-incli,  willi  rods. 

Arresters,  "  Cook  "  : 

Can  top,  type  M-8,  unfused. 

Can  top,   type  S-8,  fused. 
Arresters,  Mason's  Standard,  wiili  or  without  fust^s. 

Arre.sters,  "Sterling,"  in  strips  of  ."i  or   K)  pair,  fused,  with  carbon  arresters. 
Brackets,  oak. 
Bolts,  cross-arm,  diameter  |-inch  ;  suiiplied   in  six  lengths:    1(),    li^,  14,  16,  18, 

and  20  inches. 
Bolts  for  cross-arm  braces,  carriage,  i  indi  by  4  inches  long. 
Bolts,  double-arm    (diameter  i  inch;   lengtli,   IL',   14,  16,  or  IS  inches). 
Boxes,  junction,  3-way. 
Boxes,  telephone,  outlet,  for  rifle  ranges. 
Boxes,  telephone,  portable,  for  rifle  ranges. 
Braces,  cross-arm,  pairs. 
Brackets,  iron,  for  lance-pole  insulators. 
Cable,  aerial,  lead-covered.     (Sec  table  of  cables.) 
(^able,  telephone,  switchboard,  20-pair. 
Clamps,  strand,  2-bolt,  for  j-inch  strand. 
Clamps,  strand,  3-bolt,  for  §-inch  strand. 
Clips,  cable,  marline. 
Clips,  Crosby. 
Cleats,  cross-arm    ( wood ) . 
Cleats,  porcelain : 

2-wire. 

.3-wire. 

1-wire. 

New  England  telephdiic  cleat   with  car. 


46 


Signal  Corps  Manual  No.  3. — Chapter  8. 


Conform  aOict(/  tot/ro^,na  i 


Fig.  8-1 2.- LINE    CONSTRUCTION    MATERIAL. 


(828) 


Technical  Equipment  Issued  by  the  Signal  Corps. — Chapter  8.  47 


Mo//eab/e  /ron  orMi/dSiee/ 


Fig.  8-13.— LINE    CONSTRUCTION    MATERIAL.   MESSENGER    SUPPORT. 

(3:^9) 


48 


Signal  Corps  Manual  No.  3. — Chapter  8. 


Couiluit.  loricated  or  elect rochu-t.  A  to  2  iuelie.s.  with  couplings  and  elbows. 

Conduit,  bituminized  fiber.  B-incli. 

Conduit  elbows.     State  kind  and  size. 

Conduit  couplings.     State  kintl  and  size. 

Cross  arms,  iron  pole. 

Cross  arms,  wood  (state  number  of  pins),  bored  for  li  -inch  pins: 

Regular  telephone  size,  2^  by  3i  inches. 

Heavy  telephone  size,  3^  by  4i  inches. 

Dhncnsions  of  stfunhird  hcitvij  vroaa  (tr)iis. 


Length. 

Number 
of  pins. 

Pin  spacing. 

Ends. 

Sides. 

Centers. 

Feel, 
i 
i 
ti 

s 
10 

2 
4 
6 
8 
10 

4 
4 
4 
4 
4 

2.S 
16 
16 
16 
16 

12 
12 
12 

12 

L'orniing  strips. 

Fu.ses. 

Hangers,  cable,  marline. 

Hangers,  cable,  Locke,  2-inch. 

House  line,  liemp. 

Insulators,  pigtail,  galvanized. 

Insulators,  pony,  gla.ss   (No.  11,  double  groove). 

Insulators,  lance  pole,  pigtail,  hard  rubber  or  molded  mica. 

In.sulators,  lance  pole,  clamp,  hard  rubl)er  or  molded  mica. 

Insulators,  strain,  P.  and  S. 

Insulators,  porcelain,  standard  knobs,  as  follows: 

No.  4  (diameter,  li  inches;  length,  li^  inches). 

No.  5  (diameter,  1  inch;  length.  1^  inches). 

No.  6  (diameter,  ii  inch;  length,  |  inch). 

No.  11    (diameter,  H  inches;  length,  Ig   inch). 
Insulators,  tree,  Gem  or  Victor. 
Molding  signs. 

Molding,  type  A  (two  i  by  i  inch  grooves). 
.Molding,  type  IJ  (three  A  by  i  iiw  li  grooves). 
Molding,  type  C  (two  M  by  i  inch  grooves). 
Nails,  8d.  bntfonlM-ad. 
Ozite. 

Paint,   .Mogul,   iircscrvalixc.   gallons. 
Paraflin. 

I'ilii'.    iron.   I'-inrli.   :',-iii(li,   g;il\iini/.ci|.    per    loor. 
Pins,  insulator,  iM-inch  cross  ;irni. 
Plug.s,  Insulator  for  iron   iiolcs. 

Poles,  steel,  telegrai)h,  20  feet   long;  wcigiii,  S(i  pounds. 
Poles,  lance,  with  tip,  14  feet   long:  wfiglit,  s  ixtund.s. 
Poles,   wooden. 
Pole  steps. 


cy.m 


Technical  Equipment  Issued  by  the  Signal  Corps. — Chapter  8. 
Desired  dimensions  of  icood  poles. 


49 


Circumference  in  inches— 

For  light  line. 

For  heavy  line. 

Length. 

At  6  feet 

At  6  feet 

At  top. 

from 
butt. 

At  top. 

from 
butt. 

Feel. 

20 

1(1 

24 

16 

25 

25 

20 

30 

22 

32 

30 

20 

33 

22 

36 

35 

20 

36 

22 

40 

40 

20 

40 

22 

43 

45 

20 

43 

22 

■  47 

50 

20 

46 

22 

.50 

00 

20 

49 

22 

5:} 

60 

20 

52 

22 

56 

Ring.^,  bridle,  i-incli ;  li-incli;  ll-incli;  or  3-inch. 
Rods,  guy,  I  by  60  inclies, 
Rods,  ground. 
Sandpaper,  standard. 
Screws,  state  whetlier — 

Brass  or  iron. 

Maciiine  or  wo(k1. 

Lengtli. 

Flathead  or   roundiiead. 

Commercial  type  number. 
Screws,  lag,  state  size. 
Screws,  lag,  fetter  drive. 
Seats,  pole. 

Sumniaiy  of  parts : 

One  angle-iron  framework. 

Two  braces. 

Two  three-eighths   (|)   inch  bolts. 

Three  one-quarter   (i)   inch  stove  bolts. 

Four  one-half  (*)   inch  lag  screws. 

One  wooden  seat. 
Sleeves,  lead — order  by  inside  diameter. 
Sleeves,  paper,  A  inch  by  3  inches. 
Sleeves.  Mclntyre — state  diameter  of  wire  in  mils. 
Solder,  half-and-half,  in  bars. 

Solder,  plumber's  wiping,  in  o-pound  ingots,  40  per  cent  tin. 
Staples,  d.  p.,  "  Blake,"  No.  3.  insulated.  §-inch. 
Strand  messenger,  ^-inch  to  f-inch. 

Properties  of  stnnid. 


Diameter. 

Inch. 

I 

i 

Diameter 

of  strands 

in  mils. 

Tensile 
strength. 

162 
120 
114 
72 

57 

Pound.t. 
8,320 
4,700 
3,300 
1,750 
1,000 

46581°— It- 


(331) 


50 


Signal  Corps  Manual  No.  3. — Chapter  8. 


Strand,  guy.  i-ineh. 

Supports,  cross-arm  (for  attaching  wood  arms  to  iron  poles). 

Supports,  messenger. 

Tacks,  "  Milonite." 

Tapes.     (See  Insulating  material.) 

Thimbles,  guy,  for  :|-inch  and  §-inch  strand. 

Tags,  cable. 

Terminal,  cable  pole.      (See  Arresters.) 

Tubes,  porcelain : 

Diameter  of  bore,  rs  inch ;  length,  li  inches. 

Diameter  of  bore,  H  inch ;  length.  3  inches  and  S  inches. 
First-class  wood  poles  should  not  have  a  sweep  greater  than  as  indicated  in 
the  following  table,  the  sweep  to  be  measured  between  the  5-foot  mark  and 
the  top  of  the  pole : 

20-foot  pole,  sweep  not  more  than  2  inches. 

2.5-foot  pole,  sweep  not  more  than  3  inches. 

30-foot  pole,  sweep  not  more  than  5  inches. 

35-foot  pole,  sweep  not  more  than  6  inches. 

40-foot  pole,  sweep  not  more  than  6  inches. 

45-foot  pole,  sweep  not  more  than  7  inches. 

50-foot  pole,  sweep  not  more  than  7  inches. 
Guy  stubs  and  anehor  logs. — The  timber  used  for  guy  stubs  and  anchor  logs 
shall  correspond  in  all  respects  with  that  specified  for  poles.     Anchor  logs  shall 
not  be  less  than  24  inches  in  circumference  nor  less  than  4  feet  in  length. 
Guy  stubs  shall  not  be  less  than  22  inches  in  circumference. 
The  timbers  to  be  used  for  pole  braces  shall  be  of  the  same  quality  as  that 
specified  for  poles.     No  braces  shall  be  less  than  18  inches  in  circumference  at 
smaller  end. 

Cedar  poles. 


Size  of  pole. 

Estimated 
vveiglit  of 

Number  of 
poles  per 

Top 
diam. 

Leni,'lh. 

eacb. 

carload. 

Irwhrs. 

Feet. 

Poundi^. 

4 

20 

100 

210  to  420 

.5 

20 

130 

1S5  to  325 

0 

20 

175 

130  to  250 

7 

20 

210 

11510  200 

1 

25 

150 

Kioto  2S0 

5 

25 

200 

120  to  210 

5J 

25 

225 

110  to  190 

6 

25 

250 

KK)((i  170 

7 

25 

350 

70  to  130 

H 

25 

400 

W  to  105 

f, 

30 

275 

SO  to  155 

i; 

30 

350 

70  to  120 

7 

30 

450 

.55  to   95 

8 

30 

550 

45  to    SO 

(i 

35 

450 

70  to  no 

7 

35 

600 

50  to    70 

8 

35 

750 

40  to    (10 

6 

40 

625 

50  to    (15 

7 

40 

SOO 

40  to    55 

s 

40 

975 

30  to    45 

(332) 


Technical  Equipment  Issued  by  the  Signal  Corps. — Chapter  8. 
Cedar  poles. 


51 


Size  of  pole. 

Estimate'l 

weight  of 

each. 

Number  of 

poles  per 

load  (2  cars). 

Top 
diam. 

Length. 

Inches. 
7 

S 

s 

s 

Feet. 
45 
45 
50 
50 
55 
55 
60 
65 

Pourtd.t. 
1,000 
1,150 
1,250 
1,350 
1,550 
1,750 
2,000 
2,700 

60  to  70 
52  to  58 
48  to  55 
44  to  48 
39  to  42 
34  to  37 
30  to  33 
23  to  25 

MARKING    HAMMERS. 

Wlienevpr  insitoctions  of  f'onsi(lera])le  quantities  of  poles,  wooden  conduits, 
cross  arms,  or  otlier  rouRli  woodwork  are  required,  the  inspector  will  be  sup- 
plied with  a  niarkinjr  hammer  showing  the  crossed  flags  of  the  Signal  Corps 
and  a  letter  indicating  the  office  from  w^hich  the  inspection  was  made. 

These  marking  hammers  will  be  supplied  by  Department  Signal  Officer  or 
signal  otfice,  Washington,  when  needed. 

LINE  CONSTRUCTION   TOOLS. 

[Standard  construction  tools  as  described  in  specification  No.  360.] 

Adz.  house  carpenter's  full  head,  4-inch  blade,  Fayette  R.  Plumb's  or  American 

Axe  &  Tool  Co. 
Ax.  hand  (specified  as  broad  hatchets),  o-inch  blade.  Plumb's.  Germantown.  or 

Keen  Kutter.  • 

Axes,  handles  for.  to  be  hickory,  clear,  straight-grained. 
Ax.  lineman's  5-pound,   long-handle,   all  steel,   Plumb's.   Germantown,   or  Keen 

Kutter. 
Bags,  lineman's  best  canvas,  with  leather  bottom,  20-in<li.  letters  "  U.  S.  S.  C," 

1  inch  high,  in  indelible  ink  stenciled  thereon,  W.  E.  No.  15201. 
Bars : 

Crow,  wedge  i)oint,  17  p(miids,  best  tool  steel. 

Digging,  1  inch  round.  S  feet  long,  weight  17  pounds,  and  Is   in<-hos  romnl, 

8  feet  long,  weight  2S  pounds;  both  to  be  of  solid  steel. 
Di.uging  and  tamping,  1  inch  round  tool  steel.  7  feet  long,  weight  1!)  pounds; 

1  inch  octagonal  tool  steel,  8  feet  long,  weight  2.")  poiuids. 
Digging  (electric  spud),  steel  tubing,  with  cast  blade  and  t.iniix'r. 
Belts,  lineman's,  for  tools,  with  loops,  rings,  and  safety  strait,  as  iii-r  drawing, 

paragraph  3  (ft). 
Bits: 

Auger,  Irwin,  sizes  1-inch,   i^^-incli.  s-i'i<'l>.  s-incli,  s-inch.  4-iiuli.  all  S  iuclies 

long. 
ExpaTision.  s  inch  to  '.i  inches,  C.  E.  .Tennings's. 
Pole,  Irwin,  12  inches  by  §  inch,  and  16  inches  by  |  inch. 
Blades,  hack-saw,  10-inch,  Milford. 


(333) 


52  Signal  Corps  Manual  No.  3. ^Chapter  8. 

Blocks : 

Pulley,  Star  braiul.  Boston  <&  Lockport  Block  Co.,  galvanized  malleable 
iron,  as  follows  (all  blocks  with  one  hook  and  one  becket)  :  Single  or 
double.  3-incb  block  for  §-iuch  rope.  15-inch  sheave ;  double  or  triple, 
6-inch  block  for  |-inch  rope,  Si-inch  sheave;  double  or  triple,  10-inch 
block.  6:J-inch  sheave. 

Roller  for  cable. 
Braces,  ratchet,  8-inch  sweep,  IMillers  Falls  Co.  or  Bai'ber's  Inijiroved. 
Buffalo  grip  with  pullej's  No.  1  size,  W.  E.  Co.,  for  wires  up  to  No.  1G2  mils 

diameter. 
Chain,  cow,  4  feet,  with  rings. 
Chisels,  cold,  f-inch  to  1-inch,  tool  steel. 
Chisels : 

Socket-framing,  1^  inches  to  2  inches. 

Socket-framing,  handles  for,  ring-topped,  best  ([uality  hickory. 
Clamps,  combination  splicing,  for  wires  04  to  204  mils  diameter,  iron  ;  for  04  to 

128  mils  diameter,  copper    (for  Mclntyre  coiuiecters). 
Climbers : 

Klein's  Eastern,  16  inches  and  IS  inches,  with  straps  and  pads. 

Straps  and  pads,  for  Klein's  Eastern,  to  be  of  best  (piality  leathei'. 
Coppers : 

Soldering,  with  handles,  1  pound.  2  pounds,  and  4  pounds. 

Soldering,  handles  for,  with  ring  fei-rules. 
Cord,   Sampson  spot,  waterproof,  three-eiglitlis    (§)    inch   diameter,  in  coils  (»f 

100  feet. 
Drill,  rock,  made  of  best  tool  steel,  large  and  small  sizes. 
Files : 

Nicholson  or  Disston  ;  dentist  tile;  .'j-incli  triangular;  8-inch  round;  Hat; 
bastard  ;  half-round  ;  S-inch. 

Handles  for,  wood. 
Frames,  hack-saw,  Star  No.  10. 
Furnace,    gasoline,    with   0-inch   pot   and   S-inch    ladle,    Whilte's   or   Clayton   & 

Lambert's  No.  10,  galvanized  tank. 
Globes,  plain  or  ruby. 
Hammers : 

Claw,  18-ounce,  Maydole,  Atha,  or  Keen  Kutter. 

Machinists,  2-pound,  Maydole.  Atha,  or  Keen  Kutter. 

And  hatchets,  handles  for.  best  grade  Inckory. 
Handles  with  tools.  No.  .").  Millers  Fjills  Co. 
Hooks : 

Cant,  4-foot,  with  handl(>,  Dickie  Tool  Co. 

Carrying,  4-foot  ban<IIe,  Dickie  Tool  Co. 
Jack   strap.   comj)lete,   with    hook   an<l    No.    1    P.ulTalo   grip,   W.   E.   Catalogue, 

No.  2667. 
Kit,  tool,  inspector's  ]»ocket. 
Knives : 

Draw,  lelcgi'iiph  pattern.  12-inch  and  14-inch  bl:id(\  .lennings'. 

Electrician's,  Empire  Knife  Co.,  No.  1018. 
Lanterns,  excavation,  ruby  gl(»b('.  Dietz,  or  Ham's  tubular. 
Pick  liandles.  straight-grained  hickory.  :{(!  inches  long. 
Picks,  Iron  City  or  Klein  &  Logan's,  7  pounds  to  S  i)onnds. 
Pike,  guarded  or  raising,  14-foot. 

(:5:;4) 


Technical  Equipment  Issued  by  the  Signal  Corps. — Chapter  8.  .53 

Pliers : 

LineniaiTs,  O-incIi  sidi-  ciiltin;,'.   V.  1).   F.  i^  T.  i'o..  Sn.  ."ifj.  or  I'.  S.  &  W., 
No.  40. 

Lineman's,  .S-indi  side  cull  in;;,   L'.  1).  i<\  ifc  T.  Co.,  No.  .'"lO.  or  I'.  S.  &  W., 
No.  40. 

6-inch  diagonal,  F.  Unstroni. 
Poles,  pike,  12-foot.  lO-foot,  and  IS-foot,  2  inches  in  dianicler,  strai^lit  liv(>  ash, 

or  white  or  yellow  iiiiic  lo  suit  locality. 
Pole  support : 

Jenny,  7-foot. 

Mule,  6-foot. 
Post-hole  augers,  12-inch,  5  feet  lonu'.  Hercules. 
Post-hole  diggers,  O-foot   or  7-foot  handles. 
Reels : 

Pay-out,  with  or  without   slioulder  straps,  as  ordered. 

Take-up. 
Reel  jacks: 

Klein's  or  King's,  for  2J-inch  shaft,  capacity  10  tons  ])er  pair. 

Axes  for,  steel,  1-inch,  1  J-inch,  2-inch,  and  2i-indi. 
Rope,  pure  manila  hemp : 

|-inch,  in  coils  of  1.000  feet. 

2-inch,  in  coils  of  1,000  feet. 

§-inch,  in  coils  of  500  feet. 

f-inch,  in  coils  of  000  feet. 

1-inch,  in  coils  of  500  feet. 
Rules : 

2-foot,  folding,  boxwood,  brass  bound,  No.  62^,  C.  S.  Co. 

Zigzag,  4-foot,  Stanley  liule  &  Level  Go. 
Saws : 

Crosscut,  Disston's,  .5-foot,  willi  handles. 

Hand,  2G-inch,  No.  7.  .S-])oint.  Disston's. 

Rip,  2G-inch,  5^-point,  Disston's. 
Screw  drivers.  Perfect,  .3  inches,  4  inches,  0  inches,  and  12  inches. 
Shovels : 

6-foot  and  8-foot  handles,  with  IS-lnch  straps.  Ames's  or  (Jriflith's. 

Handles  for. 
Spades : 

Grading,  roxmd  and  square  pointed.  D  handles. 

Handles  for. 
Spoons,  6-foot  and  S-foot  bundles.  IS-inch  sti-ap.  Ames's  or  Oritllth's, 
Straps,  safety,  for  lineman's  belts. 

Tape  line,  metallic,  Lufkin,  100  feet  and  50  feet.  In  feet  and  inches,  leather  case. 
Torches,  blow,  hot  blast,  Clayton  &  Lamlierfs,  No.  P>2. 
Tree  trimmers : 

Large  size,  without  saws. 

Large  size,  with  saws. 

Handles  for,  IS  feet,  with  ferrule  joint. 
Wrench,  combination  lag  screw  and  init,  Klein's. 
Wrenches,  monkey,  Coe's.  10-inch  and  12-inch,  or  P.  S.  &  W.,  No.  100. 

Following  is  a  brief  descrii)tion  and  enumeration  of  contents  of  the  various 
instrument  and   tool   kits   which   have  been  devised   by   the   Signal   Corps   for 


(335) 


54 


Signal  Corps  Manual  No.  3. — Chapter  8. 


issue  to  construction  parties,  inspectors  and  for  use  in  maintenance  of  elec- 
trical systems.  It  is  specified  that  all  tools  furnished  shall  be  of  the  best  of 
their  kind  and  type. 

ELECTKICAL    INSTRUMENT    CASE. 

[This  electrical  case  is  manufactured  under  specification  No.  145.] 

The  electrical  instrument  case  is  issued  wherever  an  extensive  cable  system 
is  installed  or  whenever  exhaustive  and  accurate  tests  of  cable  aiv  desii-cd. 
The  case  is  of  oak,  reinforced  at  corners  with  metal.  Fiiiure  S-14  illustrates 
this  case.  For  description  and  use  of  instruments  containtMl  in  the  electrical 
instrument  case,  see  chapter  4  of  this  IManual. 

CtlXTENTS. 

1  insidation  and  capacity  test  set,  consisting  of  the  following: 

1  portable  galvanometer  «»f  the  D'Arsonval   typts  coiil'onniiig  to  drawing 

No.  nsb. 

1  telescope  and  scale  for  above  galvanometer. 

1  100,000-ohm  box. 

1  combined    shunt    and    switch. 

]   condenser  set. 

1   ohnnneter. 

1    iripod   (external  to  case). 

1  service   testing  batlery,  drawing  No.   109,  specification   No.   ISH. 

1  micrometei'  calijter,  V>.  tSc  S..  NH.  S,  withoiil  rntcliet  slop,  with  morocco- 
carrying  case. 

1    ins])ector's  ])ock('t  tool  kit,  as  jicr  drawing  \o.  1104,  specilicat ion   No.   ISO. 

1  testing  telei)hone,  to  be  furnished  by  tlic  Tnited  States  Signal  ('ori)S, 
space  to  Ite  ]>rovided  by  the  contractoi',  as  per  drawing. 

]   space   for   foi-ms  and   rei>orts. 

1  si»ace  for  books. 

.MI.S(HI,I,.\NEOI-S    PARTS    AND    SITPLIES. 


1  galvanometer  coil   and    mii-ror. 
4  round-head  plugs. 

6  lower  suspensions. 
6  upi)er  suspensions. 

2  milled-head  screws. 
]   piece  felt. 

4  screws  for  glass. 
]  ohnnneter  card. 
]   jtiece  chamois. 
1  bottle  vaseline. 
1  bottle  tyjH'writer  f>ll. 


](HI  feet  No.  22  bare  copper  wire 

]00  feet  advance  wire,   No.  28. 

25  feet  No.  22  manganin  wire. 

3.50  feet  No.  34  manganin  wire., 

300  feet  No.  40  manganin  wir(>. 

GO  feet  No.  28  manganin  wire 

1   glass  window. 

4  paper  scales. 

0  feet  battery  cord. 

10  feet  okonite  wire. 

N  ounces  solder. 


REPAIR   KIT. 


Tlic  r('i>air  kit   <'ontains  the  following  instruments: 

."'  lower  susjiensions  for  galvanometer. 
4   npiK-r  susi»snions  for  galvanomet«'r. 


1  nickel-plated   screw   driver. 

2  jiairs  tweezers,  nickeled. 


(.^.".0) 


Technical  Equipment  Issued  by  the  Signal  Corps. — Chapter  8.  55 

ilKCIIANICS'  TOOL  CHKSTS. 

[These  chests  are  manufactured  under  specification  Xo.  562.] 

Mechanics'  tool  chests  are  for  issue  to  Signal  Corps  field  companies  for  use 
in  connection  with  the  repair  of  apparatus.  There  are  two  chests,  differing 
slightly  in  dimensions  and  equipment,  and  are  designated  "  Mechanic's  tool  chest 
No.   1  "  and  "  Mechanic's  tool  chest  No.  2."     They  are  constructed  of  heavy, 

straight-graiiuHl    oak,    substantially    reinforced    at    corners    with    metal    corner 
braces. 


Fig.  8-14.— CASE,    ELECTRICAL   INSTRUMENT. 


Name  plate. 


For  Chest  No.  1— 

Mechanic's  Tool  Chest, 

Number  One, 

Field  Company, 

Signal  Corps,  U.  S.  Army. 

Serial  No. . 


For  Chest  No.  2— 

Mechanic's  Tool  Chest, 

Number  Two, 

Field  Company, 

Signal  Corps,  U.  S.  Army. 

Serial  No.  . 


The  chests  are  fitted  with  Corbin  padlock  No.  2882,  or  equal,  no  two  of  which 
have  keys  alike,  except  the  two  locks  for  No.  2  chest,  which  shall  be  opened  by 
the  same  key.     A  duplicate  set  of  keys  is  furnished  for  each  lock. 

With  the  exception  of  items  marked  (*)  each  tool  is  stamped  with  the  numlier 
assigned  to  it  in  the  following  list. 

The  chests  are  equipped  and  tools  distributed  as  follows: 

Chest  No.  1. 


Lid. 


1.  1  frame,  hack-saw,  Star,  No.  10. 


(337) 


56 


Signal  Corps  Manual  No.  3. — Chapter  8. 


Top  of  chest. 

2.  1  pliers,  side-cuttinfr,  6  inches.  U.  D.  F.  &  T.  Co.,  No.  50.  or  P.  S.  &  W., 

No.  40. 

3.  1  pliers,  diagonal,  6  inches,  F.  Linstrom,  No.  842. 

4.  1  pliers,  long-nose,  5*  inches,  U.  D.  F.  &  T.  Co.,  No.  654. 

5.  1  shears,  metal,  AV.  H.  Compton,  "  Reliance,"  No.  10. 

6.  1  hammer,  riveting,  4  ounces,  Maydole,  cast  steel. 

7.  1  oil  can,  bicycle  or  pocket  type,  24  inches  diameter,  3 -inch  thick,  curved, 

spout  with  screw  cap. 

8.  1  drill,  hand,  Goodell  Pratt  Co.,  No.  54. 

9.  1  vise,  adjustable  jaw,  swivel  base,  2-inch  jaws.  No.  37,   Prentiss. 
10.  1  screw-driver  set,  Yankee,  No.  100, 

*11.  1  drills,  twist,  set  of  60,  straight  shank,  ]\Iorse,  Nos.  1  to  60. 


Fig.  8-15.— CHEST,   TOOL.    MECHANICS    NO.  2. 

End  of  (licit. 

12.  1  torch,  gasolene,  Clayton  &  Lanilicrt.  No.  IV2. 

13.  1  grinder,  hand,  with  1  hy  5  indi  Norton  gi-inding  wln'cl,  .\iiierican,  No.  2. 

Draiocr  Xo.  J. 

14.  1  screw-plate  .set.  Little  (Jiant,  No.  A  A  4. 

15.  1  square,  conil)lnation,  0-inch  blade  without  cciilcr  licad.  Alliol,  No.  4. 

16.  1  oilstone,  mounted,  8-inch  .soft,  Arkansas,  Pike's. 

17.  1  screw  driver,   machinist's,   swivel   head,   5   inclics.   .-j^-incli   blade,    I'ii-iiich 

handle,  Syracuse. 
IS.   1  chisel,  cold,  ^-incli,  (I  inches  hnig,  "Diamond  I'dge." 
19.  2  center  punches,  straiglit-shanlc,  Syracuse,  No.  16. 
*20.  4  file.s,  4-lnch,  round. 
*21.  4  tiles,  4-incli,  square. 
*22.  6  liles,  O-inch.   rounil. 

(338) 


Technical  Equipment  Issued  by  the  Signal  Corps. — Chapter  8.  57 

23.  1  handle,  file,  malleable  iron.  1.  X.  L. 

24.  1  iron,   soldering,  i   pound. 

25.  1  iron,  soldering,  1*  pounds. 

Draicer  No.  2. 

26.  6  files,  8-inch,  flat,  bastard,  "Arcade  U.  S.  A." 

27.  1  file  cleaner.  Col  ton's  No.  10  or  similar. 

*28.  2  hack-saw  blades,  dozen,  12  inches,   Disston's. 

.  Chest  No.  2. 
Cover. 

1.  1  saw,  hand,  10-point,  Disston's,  26-inch. 

2.  1  saw,   rip,  6-point.   Disston's,  28-inch. 

3.  1  square,  24-inch,  Russell  iK:  Erwin,  No.  14    (short  end  cut  to  14  inches). 

4.  1  rule,   Stanley.  No.  104. 

Top  of  chest. 

5.  1  wrench,  monkey,  l.'i-inch.  1'.  S.  i^  W. 

6.  1  wrench,  monkey,  6-inch.  P.   S.  &  W. 

7.  1  wrench,  Stillson,  14-incli. 

8.  1  screw  driver,  7-inch,  "  Champion." 

9.  1  screw  driver,  5-inch,  "  Champion." 

10.  1  nail  puller,  "  Little  Giant." 

11.  1  knife,  draw,  8-inch,  A.  J.  Wilkinson  &  Co.,  Boston,  fohlinc:  type. 

12.  1  hannner,  riveting,  8-ounce,  Maydole,  cast  steel. 

13.  1  hammer,  claw,  Maydole,  Hi. 

14.  1  tape,  steel,  100-foot,  Lufkin's  "The  Itival." 

15.  1  brace,  10-inch,  Millers  Falls  Co. 

16.  1  chisel,  set  of  5,  If,  li,  |,  f,  and  ^  inches.  .Tennings's  No.  70. 

17.  1  calipers,  pair,  4-inch. 

18.  1  dividers,  pair.  6-inch,  V.  S.  tJc  W..  wing  or  eciual. 

Loin  r   (Iraircr. 

10.  1  screw  plate,  .set.  Conant  iV:  Donaldson  ( 'o.'s  "Reliable."  No.  3.^. 

20.  1  plane,  jack.  2-inch  bit,   Stanley. 

21.  1  plane,  block,  Ig-inch  bit,  Stanley. 

22.  1  oilstone.  Pike,  .soft  Arkansas,  o-inch.  mounted. 

23.  1  saw,  set,  Morrill's,  No.  11. 

I'pper  draicer. 

24.  1  file  holder.  I.  X.  I..,  malleable  iron. 

25.  1  file  cleaner,  Colton's  No.  10,  or  similar,  metal  back. 

'■26.  1  drill,  twist,  bit  stock,  set  of  9,  3  each  of  ^,  t^,  and  i  inch  diameter. 
*27.  1  files,  set  of  14,  Nicholson,  three  8-incli,  half-round,  smooth ;  three  8-inch. 

half-round  bastard ;  two  8-inch,  flat  bastard ;  six  6-inch  saw  files. 
*28.  1  bits,  set  of  14;  13  Irwin's  i-inch  to  1-inch  by   i^-inch.  and  1  bit,  C.  E. 

Jennings's  expansive,  J  to  3  inches. 
The  last  three  items  will  be  incased  in  canvas  rolls.     Theso  canvas  rolls  are 
to  be  neatly  and  strongly  made  of  10-ounce  Idiaki  canvas,  leather  bound,  with 
flap  and  1-inch  strap  and  buckle.     The  roll   for  the  twist  drills  shall  be   19 

(339) 


58  Signal  Corps  Manual  No.  3. — Chapter  8. 

inches  long  when  opened  out.     The  roll  for  the  files  shall  be  27  inches  long 
when  opened  out.     The  roll  for  the  bits  shall  be  36  inches  long  and  shall  have 
a  small  leather  pocket  securely  sewed  on  the  inside  for  the  extra  cutters  of  the 
expansive  bit. 
29.  1  hatchet,  half,  with  handle,  Germantown  No.  2,  thin  blade. 

AEROPLANE   TOOL   CHEST. 

[These  chests  are  luanufactiire'l  under  specification  Xo.  .^62.] 

The  aeroplane  tool  chest  is  for  issue  to  aeronautical  companies  or  detach- 
ments detailed  in  connection  with  aeronautical  woi-k.  The  chests  are  identical 
with  mechanic's  tool  chest  No.  2,  except  that  certain  partitions  are  omitted. 

Name  plate. 

Aeroplane  Tool  Chest. 

Signal  Corps,  U.  S.  Army. 

Serial  No.  . 

contk;xts. 
Colder. 

1.  1  saw,  hand,  lO-point,  Disston's,  2G-inch. 

2.  1  hammer,  riveting,  S-ounce,  Maydole. 

3.  1  combination  square,  lievel  and  level,  12-iiich,  Athol. 

4.  1  rule,  Stanley,  No.  104. 

5.  1  hack  saw  frame.  Millers  Falls  C(».,  No.  6. 

6.  1  dividers,  pair,  (i-iucli,   I'.  S,  &  W. 

Top  II f  Clteat. 

7.  1  wrench,  Stillson,  14-inch. 

8.  1  screw  driver,  7-incli,  Perfect. 

9.  1  screw  driver,  5-inch,  Perfect. 

10.  1  nail  puUei-,  Little  Giant. 

11.  1  knife,  draw,  8-inch,  A.  J.  Wilkinson  &  Co.,  Boston,  folding  type. 

12.  1  hammer,  tinsmith,  1-pound,  Atha. 

13.  1  hammer,  claw,  Maydole. 

14.  1  tape,  100-foot,  steel,  Lufkins  "  The  Rival." 

15.  1  brace,  10-inch,  Millers  Falls  Co.,  No.  32. 

16.  1  iron,  soldering,   14-pounds;  1   iron,  soldering,  jeweler's.  No.  1;  2  center 

punches,  4-inch,  Syracuse;  24  blades,  hack  saw,  10-inch,  coarse.  Star; 
12  blades,  hack  saw,  10-inch,  Star,  No.  20;  1  chisel,  cold,  4-incli,  Village 
Blacksmith;  1  chisel,  cold,  i-inch,  Village  Blacksmith. 

17.  1  screw  driver,  8-inch,  Perfect. 

18.  1  calipers,  double,  6-inch,  Starrett,  No.  44. 
10.  1  wrench,  monkey,  6-inch,  P.  S.  &  W. 

lljiixr  Draivcr. 

20.  1  bit,  ().  Vj.  .Icnning's  expansive,   I   iricli   to  ',i  inch,  with  leat^iiM*  pocket  for 

cutter. 

21.  1   pliers,  round   nose,  6-incii.   I'.crniird. 

22.  1  pliers,  stni)e  n(»se,    l-iiicli,   I'.crinrd. 

(.".40) 


Technical  Equipment  Issued  by  the  Signal  Corps. — Chapter  8.  59 

23.  1  pliers,  adjustable,  S-inch,  Danielson. 

24.  1  pliers,  side  cutting,  8-incii,  Utica,  No.  50. 

25.  1  pliers,  adjustable,  6-inch,  Danielson. 

2G.  1  pliers,  Auto,  6-inch,  combination,  cutting,  Kraeuter  &  Co. 

27.  1  pliers,  Auto,  8-inch,  combination,  cutting,  Kraeuter  &  (Jo. 

28.  1  nipper-cut.  No.  1,  Starrett,  7-inch  M. 

20.  1  pliers,  G-inch,  diagonal.  No.  842,  Linstroiu. 

30.  1  pliers,  6-inch,  diagonal.  No.  842,  Linstroni. 

31.  1  pliers,  compound,  S-inch,  side  cutting.  No.  502,  Vulcan. 

32.  1  file  holder,  I.  X.  L.  '  . 

33.  1  pliers,  S-inch,  adjustable,  Danielson. 

34.  1  spoke  shave,  3-inch,  No.  80,  Sargent ;  and  1  file  cleaner,  Colton's  No.  10. 

35.  2  files,  smooth,  S-inch,  half-round;  1  file,  bastard,  8-inch,  half-round;  2  files, 

bastard,  8-inch,  flat ;  2  files,  saw,  6-inch ;  1  file,  bastard,  10-inch ;  1  file, 
round,  G-inch;  1  file,  bastard,  S-inch,  square  (all  Nicholson  files)  ;  to  be 
contained  in  a  roll  27  inches  long  and  13^  inches  wide,  consisting  of  10 
pockets  7  inches  deep  with  a  flap  9  inches  wide  and  20  inches  long, 
pockets  extending  over  20  inches  to  take  the  files  specified.  This  roll  and 
the  rolls  for  items  42  and  43  shall  be  made  of  10-ounce  cotton  duck, 
khaki  shade,  all  edges  leather  bound,  to  be  fastened  with  straj)  and  buckle. 

30.  1  screw  driver,  4-in(h,  Perfect. 

37.  1  wrench,  bicycle,  5-inch,  Billings  &  Spencer. 

.38.  1  wrench,  bicycle.  .5-incli,  Billings  &  Spencer. 

39.  1  palm,   sewing;    two   4-incli    sailmaker's   needles;    six   4-inch,   one-quarter 

curve,  needles;  1  ball  Irish  flax,  Barbour's  No.  3,  2-ounce;  1  ball  wax. 

l.oircr  (Iraircr. 

40.  1  stone,  5-inch  Carborundum,  combination.  No.  Ill,  in  wood  case. 

41.  1  torch,  gasoline,  flat,   Clayton  Lambert  No.  48    (fastened  by  strap  with 

buckle). 

42.  1  .set  thin  open-end  wrenches,  set  of  4  Ronson  I  to  if  and  1  J.  P.  Williams 

No.  30.  to  be  contained  in  a  roll  27  inches  by  11  inches,  consisting  of  eight 
pockets  4J  inches  deep,  extending  over  20  inches  to  take  the  wrenches 
specified,  with  a  flap  to  cover  the  pockets  20  inches  by  9  inches,  the  ma- 
terial to  be  as  described  in  item  35. 

43.  1  set  drills,  Morse,  straight  shank,  Nos.  1  to  45,  inclusive ;  1  drill,  f -inch ;  1 

drill,  |-inch ;  and  1  drill,  ^fij-inch ;  to  be  contained  in  a  roll  27  inches  by 
8  inches,  consisting  of  11  pockets  to  take  large  drills,  extending  over  15 
inches,  with  a  flap  21  inches  with  a  piece  on  under  side  for  pockets  to 
take  drills  Nos.  1  to  4.5,  the  material  to  be  as  described  in  item  35. 

44.  1  plane,  block,  If-inch,  Stanley  No.  110. 

45.  1  drill,  hand,  Yankee  No.  1545. 

46.  1  wrench.  7-inch.  Billings  &  Spencer. 

47.  3  reamers,   taper,   bit  stock,   Wiley   Russell   "  Lightning."   one    1-inch ;   one 

^-inch ;  one  f-inch. 

48.  1  hatchet,  half.  No.  2,  thin  blade.  Germantown  No.  316. 

49.  1  snips,  tinner's.  Reliance  No.  10. 

The  following  list  enumerates  the  tool  kits  furni.shed  by  the  Signal  Corps 
for  use  in  the  installation  of  fire  control,  telephone,  and  small-arms  signaling 
systems,  or  for  any  construction  work  where  its  magnitud(»  warrants  such  an 
issue.     When  used  for  such  purposes  they  should  invariably  be  returned  to  a 

(341) 


60 


Signal  Corps  Manual  No.  3. — Chapter  8. 


Signal  Corps  supply  depot  when  they  have  served  the  purpose,  unless  specific 
authority  for  their  retention  has  heen  issued.  Some  of  these  kits  are  also 
issued  for  use  in  connection  with  maintenance  of  systems : 


Electrical  engineer's  tool  chest. 
Construction  tool  chest. 
Cahle  splicer's  chest. 
Pipe  fitter's  chest. 


Post  tool  chest. 
Service  tool  hag. 
Inspector's  pocket  kit. 


The  electrical  engineer's,  construction,  and  post  tool  chests  are  constructed 
of  the  hest  selected  oak  or  ash  lumber,  thoroughly  seasoned.  The  ends  and 
sides  of  these  chests  are  joined  by  dovetailed  joints,  and  the  chests  are  fitted 
with  steel  or  malleable-iron  corner  irons,  wrought-ii'on  hinges,  heavy  brass 
hasps,  and  heavy  brass  drop  handles. 

The  cal)le  splicer's  and  pipe  fitter's  tool  chests  are  coiistructcil  of  sheet  ste(>l, 
reinfoi'ced  with  hardwood  strips  and  nialleablc-iron  fittings. 


KI.ECTKICAT.    EXOT^'EER  S    TOOT.    CHEST. 

[This  i-hest  is  inauufactiiri'd  uuilcr  siicrifications  X< 


192] 


This  chest,  shown  in  figure  8-lG,  is  issued  to  electrical  experts  of  the  Signal 
Corps,  or  to  any  person  in  responsible  charge  of  fire-control  or  post-telephone 
construction  work. 


Fig.  8-16.— CHEST,   TOOL,    ELECTRICAL   ENGINEERS. 
(342) 


Technical  Equipment  Issued  by  the  Signal  Corps. — Chapter  8.  61 

Upon  appi'oval  of  the  Chief  Signal  OfHcer  of  the  Army  tliis  c-liest  is  also 
issued  to  coast  defense  Artillerj-  Engineers  of  large  coast-defense  commands 
for  use  in  maintaining  the  fire-control  and  post-telephone  systems. 

The  chest  contains  a  full  complement  of  tools  necessary  for  the  installation 
of  apparatus. 

Xante  ijlutc. 

El.ECTlIIC  Al.    KXGINEKU'S    ToOL    <  'HEST. 

U.  8.  Signal  ("okps. 

No. . 

The  tools  are  distributed  as  follows: 

C'orcr. 

1.  1  Itacksaw,  l(t  inches.  Xo.  1,  Di.sston's. 
12.  1  rule,  4-foot.  S-fold,  Stanley.  No.  404. 

3.  1  crosscut  saw,  20  inches,  9  teeth  per  inch,  Disston.  No.  7. 

4.  1  ripsaw,  22  inches,  6  teeth  per  inch,  Disston,  No.  7. 

5.  1  hack-saw  frame,  Star,  No.  10. 

G.  1  tape,  metallic,  50  feet,  Lufkiii  Uulc  ('o..  No.  .jU3. 

First   trinj. 

7.  1  .spirit  level,  pocket,  3-inch,  No.  31,  Stanley's. 

8.  1  polarity  indicator,  Manhattan,  M.  E.  S.  Co.,  No.  3321. 

9.  1  wrench,  Athol  ^Manufacturing  Co.,  "  Rapid  Transit,"  G  inches,  black,  No. 

541. 

10.  1  hammer,  riveting,  15  ounces,  "  Atha."  No.  234. 

11.  1  hanuner,  claw,  1  pound,  "  Atha,"  No.  41*. 

12.  1  jackknife,  "Empire,"  AVinsted,  Conn.,  No.  1013. 

13.  1  screw  driver,  5  inches,  "  Perfect." 

14.  1  screw  driver,  10  inches,  "  Perfect." 

l."i.  1  chisel,  socket,  1-inch,  "Jennings,"  No.  70. 
IG.  1  chisel,  socket,  i-inch,  "  Jennings,"  No.  70. 

17.  3  tiles;  two  8-inch  flat  bastard,  one  8-inch  clear  edge,  hand,  bastard.  "Arcade, 
U.  S.  A." 

15.  1  chisel,  cold,  i-inch,  G  inches  long. 

19.  1  screw  driver,  2  inches.  Tucks  Giant. 

20.  1  screw  driver.  2^  inches.  No.  825.  O.  W.  Bullock  &  Co. 

21.  1  tool  holder  with  tools.  Millers  Falls  Co.,  No.  5. 

-   Second  tiaii. 

22.  1  dividers,  pair.  6-inch,  P.  S.  &  W.  wing,  or  eciual. 

23.  1  ratchet  brace.  Millers  Falls  Co..  8-inch  throw.  No.  33. 

24.  2  buffalo  grips,  with  pulleys,  one  each.  Nos.  1  and  2.  W.  E.  Co. 

25.  1  scale,  12-inch,  combination  square  (Athol).  No.  500.  12-inch  set.  complete. 
2G.  1  center  head,  combination  .square  (Athol).  No.  5(K).  12-inch  set,  complete. 

27.  1  square  and  bevel,  combination  square  (Athol),  No.  500,  12-inch  set,  com- 

plete. 

28.  1  vise,  hand  (Atlutl).  No.  .549,  H  inches. 

29.  1  plane,  block,  Stanley.  No.  130. 


(343) 


62  Signal  Corps  Manual  No.  3. — Chapter  8. 

30.  1  shears,  pair,  metal,  W.  H.  Compton  "  Reliance,"  No.  10. 

31.  1  soldering  copper,  jeweler's,  No.  2. 

32.  1  soldering  copper.  1  pound. 

33.  1  soldering  iron,  electric.  No.  10,  American  EU;clric  Heater  Co.,  with  Edison 

attachment  plug. 

Tlilnl  tray. 

34.  1  oilstone,  "  Pike,"  soft  Arkansas,  5-inch,  mounted. 

35.  1  pliers,  pair,  8-inch,  side-cutting,  U.  D.  ¥.  &  T.  Co.  No.  30.  or  P.  S.  &  W. 

No.  40. 

36.  1  ladle.  3-inch,  wrought-iron  handle. 

37.  1  pliers,  pair.  5i-inch.  long  nose,  side-cutting.  U.  D.  F.  &  T.  Co.  No.  o54. 

38.  1  monkey  wrench,  Coe's  12-inch,  or  Bemis  &  Call's  No.  54,  or  P.  S.  &  W. 

No.  100. 

39.  1  nail  puller.  Little  Giant. 

40.  1  wrench,  Stillson,  14-inch. 

41.  1  pliers,  pair,  6-inch,  side-cutting,  U.  D.  F.  &  T.  Co.  No.  50.  or  P.  S.  &  W. 

No,  40. 

42.  1  i)liers,  pair,  diagonal  cutting,  6-inch,  No,  842.  F.  Linstrom. 

43.  2  clami^s,  combination  splicing,  Klein,  No.  309. 

Fourth  tray. 

44.  1   countersink,  wood,  C.  E.  Jennings,  No.  001. 

4.5.  9  drills,  steel  twist,  i-inch,  A-inch,  §-inch,    ilj-inch,  1-inch;  Nos.  2,  12,  22, 
and  30,  and  1  center  punch,  No.  16  Syracuse;  straight  shank,  standard. 

46.  1  punches,  set,  alphabet,  ^-inch. 

47.  1  plumber's  kettle,  5  inches. 

48.  1  drill,  breast,  Millers  Falls,  No.  18. 

49.  2  shields  for  fire  pot. 

50.  1  figures,  set,  steel,  J-inch. 

51.  1  bit,  expansion,  2  cutters,  |-inch  to  3  inches,  Clarke's. 

52.  1  plane,   rabbet,   ^-inch. 

53.  1   knife,  cable  sheath,  4i-inch  bhuUs  "  Vilhig(>  Blacksmith,"  IMilwaukee. 

54.  1  bits,  set  of   Irwin   auger,  with   4-iuch  triangular  tile,    fc-inch   to   1-iuch 

by   sixteenths. 

IU\(l  of  chcHt. 

.55.    1    riiniiice,  Chiyloii  i\:    Lanihci-I's,   No.    1(t,   gai\aiii/,e(l    t;mk. 

.56,    1    liii»'nian"s  magneto  lesting  s(M    (  rurnislicd  by  V.   S.  Signal  Corps). 

57.    1    hack-saw  blades,  dozen,  all    liard,    10   inches,   Milford. 

(•oNsri;r(  rioN    rooi,  (  iii:si'. 
I'l'liis  chrsl   is  miimifncliii-cil  iindiT  spcciliciliiiti   Ni>.    loo.  | 

The  eonslniction  tool  chest,  figure  8-17,  is  issued  lo  any  jterson  in  resixmsi- 
ble  ciiarge  of  lii-e-conl  rol  or  i)ost-leh'i)hone  construclion  work,  and  upon  ap- 
jtroval  of  the  ("liief  Signal  ( XlictM"  of  (he  .\rmy  is  issued  for  use  in  connection 
with   maintenance. 

While  this  cJiest  is  larger  in  size  than  the  electric.nl  engineer's  tool  cli(>st, 
it  does  not  contain  so  great  an  assortment  of  tools. 

It  is  iiarticularly  adapted  for  use  where  construction  or  mainteniince  of 
aerial  lines  is  concerned. 


(344) 


Technical  Equipment  Issued  by  the  Signal  Corps. — Chapter  8.  63 


Fig.  8-17.— CHEST,  TOOL,  CONSTRUCTION. 

Name  plate. 

Construction  Tool  Chest. 

U.    S.    Signal  Cokps. 

Xo.  . 

This  chest  shall  be  proviileil  with  Corbiu  lock  Nu.  2882,  or  equal,  and  dupli- 
cate set  of  keys. 

2  axes,  hand,  4J  inches,  Germantown. 
1  bag,  tool,  service,  empty. 

1  bit,  bellhanger's,  24  by  f  inches,  Syracuse,  style  E. 

2  bits,  sets,  Irwin,  in  boxes  (25A),  quarters. 

3  blades,  hack  saw,  10-inch,  Milford,  dozen. 

1  box,  miter.  Perfection. 

2  braces,  Millers  F'alls,  No.  33. 

2  chisels,  wood,  1-inch,  .Tenniiigs,  No.  70,  socket. 

2  coppers,  soldering,  with  handles,  2i  pounds.  . 

1  copper,  soldering,  with  handle,  jeweler's.  No.  1. 

1  dies,  marking,  steel,  figures,  ^-inch,  hand  cut,  sot. 

1  dies,  marking,  steel,  letters,  i-inch,  hand  cut,  set. 

1  drill,  breast,  Jlillers  Falls,  size  No.  18. 
12  drills,  rock,  t\;-inch,  Star. 

12  drills,  rock,  tk-inch.  Star. 

7  drills,  twist,  straight  .<hank,  ^  to  i  inch  in  sixteenths,  standard. 

8  files,  assorted,  with  handles;  2  bastard,  half-round,  10-inch;  2  hand,  safe 
edge,  6-inch;  2  slim  taper  saw  tiles,  oj-inch ;  1  round  file,  6-inch;  1  rasp, 
cabinet,  10-inch,  Genuine  McCaffrey  ;  2  frames,  hack  saw,  Star,  No.  10. 

2  gouges,  f-inch,  Jennings,  No.  91,  socket. 

2  grips,  buffalo,  one  each  Nos.  1  and  2,  W.  E.  Co.,  with  pulleys. 

(.345) 


64  Signal  Corps  Manual  No.  3. — Chapter  8. 

6  hammers,  claw,  carpenter's,  15-ounce,  No.  41i,  Atha. 

6  holders,  tool,  with  tools,  Millers  Falls  Co.,  No.  5. 

1  indicator,  polarity,  M.  E.  S.  Co.,  No.  3321. 

2  kits,  tool,  inspector's  pocket. 

1  knife,  cable,  sheath,  4i-inch  blade,  "  Village  Blacksmith."  Milwaukee. 

6  knives,  P^mpire,  No.  1013. 

1  mallet,  serving,  metal. 

1  mallet,  wooden. 

1  oilstone.  Pike,  soft,  Arkansas,  5-incli,  mounted. 

1  plane,  block,  li-inch  blade,  Stanley,  No.  220. 

1  plane,  fore,  2i-inch  blade,  Union  Manufacturing  Co.'s  No.  28. 

1  plane,  jack,  2-inch  blade.  Union  Manufacturing  Co.'s  No.  26. 

1  plane,  rabbet,  J-inch  blade.  Union  Manufacturing  Co.'s  No.  157. 

2  pliers,  diagonal,  cutting,  6-inch,  pairs,  F.  I^instrom,  No.  842. 

1  pliers,  gas,  S-inch,  P.  S.  &  W.,  pair. 

2  pliers,  side-cutting.  6-inch,  U.  D.  F.  &  T.  Co.  No.  50.  or  P.  S.  &  W.  No.  40. 
2  pliers,  side-cutting,  8-inch,  U.  D.  F.  &  T.  Co.  No.  50,  or  P.  S.  &  W.  No.  40. 
2  pliers,  long-nose,  5i-inch,  U.  D.  F.  &  T.  Co.  No.  654,  pairs. 

1  punch,  center,  Syracuse,  No.  16. 

2  saws,  back,  10-inch,  Disston's. 

1  saw,  compass,  12-inch,  Disston's. 

1  saw,  crosscut,  carpenter's,  20-inch,  Disston's.  0  points.  No.  7. 

1  saw,  rip,  carpenter's,  22-incli,  Disston's,  6  points,  No.  7. 

2  screw  drivers,  12-inch,  Perfect. 

1  shears,  8-inch,  pair,  straight  trinnners.  Compton. 
1  snips,  pair,  No.  10,  Compton. 

1  tape,  50-foot,  metallic,  Uufkin,  No.  503. 

2  torches,  gasoline,  Clayton  &  Lambert,  No.  32. 
1  try-square,  steel,  6-inch,  Stanley,  No.  12. 

1  wrench,  screw,  12-inch,  Coe's  or  Bemis  &  Call's,  No.  54. 
1  wrench.  Stillson,  14-inch. 

CABLE  splicer's  CHEST. 

I  This  clii'sl  is  manufactured  undor  sp(^cilication  No.  .S18.] 

Tliis  cliest.  shown  in  figure  8-18,  includes  nil  lools  necessary  for  Ihc  splicing 
of  cal)i(^,  together  with  one-(iuartor  pound  stearino,  1  pound  of  ginmned  paper, 
250  i)ai)er  sU'cvos  three-sixteenths  inch  by  3  inches,  and  two  cotton  strips  one- 
fourth  inch,  in  rolls  5  inches  in  diameter.  De))endence  can  not  be  placed  in 
the  cliest  containing  the  expendable  articles  listed  above  unless  it  is  supplied 
directly  from  a  Signal  Corps  supply  depot. 

Name  pidtc. 

Caiu.e  Siujcek's  Chest, 

U.  S.  Si(i.\.\i.  ( 'oiu's. 

No. . 

Equipment. 

1   plumber's  furna<e,  wilh  two  <liinuieys.  No.  1(»  ('.  iV  L.  Mfg.  Co.    (galvanized 

tank ) . 
1   ladle,  3  indies,  W.  T.,  with  wrought-iron  handle. 
1   inspector's  pocket  kit. 

(.•!46) 


Technical  Equipment  Issued  by  the  Signal  Corps. — Chapter  8.  65 


Fig.  8-18.— CHEST,  TOOL,   CABLE   SPLICERS. 

1  hotik  shave,  No.  949,  oval,  A.  S.  Morse  Co. 

1  plumber's  kettle,  5  inches. 

2  soklerins  coppers,  2i  and  4  ixiunds.  with  haiidk'.s. 

1  knife,  cable,  sheath,  4i-incli  blade,  "  Villa,u.e  Blacksiniih."  Milwaukee. 

1  saw,  plumber's,  Disston's,  14  inches. 

1  hack-saw  frame,  "  Star."  adju.stable.  No.  It). 

2  hack-saw  blades,  10  inclies,  dozen,  Milford. 
1  cable  dresser,  dogwood. 

1  stearine,  i  pound,  in  metal"  can. 

1  paper,  gummed,  li  inclies  wide  ("Paster's'"),  iioiuids. 

1  luunmer,  claw,  with  handle,  Atha,  No.  414. 

1  hanmier,  plumber'.s,  18  ounces,  with  handle.  No.  24(»(/  Atha. 

1  tool  bag,  canvas,  leather  bottom,  20  inches,  \V.  E.  Co..  No.  l.">201. 
2.'>0  paper  sleeves,  -us  inch  by  3  inches. 

2  cotton  strijts,  1-incli,  in  rolls,  5  inches  diameter. 

()  cloths,  wiping,  moleskin,  two  6  inches  .square;  two  3  inches  s(iuare;  and  two 

5  inches  square. 
1  file,  hand,  smooth,  6  inches,  with  handle. 
1  tile,  half-round,  bastard,  6  inches,  witli  liaiidli'. 
1  rasp.  12  inches,  with  handle,  cabinet. 

1  rule,  2-foot,  folding,  boxwood,  brass  bound.  No.  (ViJ.  C  S.  Co. 
1   i>lit'rs,  pair.  S  inches,  X\  D.  F.  &  T.  Co.,  No.  50.  or  1'.  S.  &  W..  No.  40. 
1  snips.  No.  10.  Comptou. 

3  drift  pins,  1]  inches,  14  inches,  2  inches. 

1  torch,  gasoline.  Clayton  &  Lambert,  No.  32. 

rii'K  kittkr's  chest. 

[This  chest  is  niainffactiireil  imdcr  specification  No.  276.] 

The  pipe  fitter's  chest  is  issued  whenever  work  in  connection  with  fire-control 
or  post-telephone  systems  require  the  installation  of  iron  conduit.  Tools  neces- 
sary in  cutting  and  threading  iron  conduit  from  one-half  to  2  inch  sizes  are  in- 
cluded in  the  equipment  f)f  this  chest.  The  chest  also  contains  a  pipe  former, 
for  use  in  bending  iron  conduit  in  sizes  from  one-eighth  inch  to  IJ  inches. 
This  chest  is  shown  in  figure  8-19. 

465S1°— 17 23  (347) 


66  Signal  Corps  Manual  No.  3. — Chapter  8. 


Fig.  8-19.— CHEST,   TOOL,    PIPE    FITTER'S. 

Naiiic  plate. 

Pipe  Fitter's  Chest, 

U.  S.  Signal  Coups. 

No. . 

Eilitipiiiciil. 

2  pipe  wrenches,  "  Trimo,"  IS  inches. 

1  pipe  vise,  combination,  Prentiss,  swivel  base,  Sl-inch  reversible  jaws. 

1  pipe  cutter,  "  Trimo,"  No.  2,  i  inch  to  2  inclies. 

1  stock  for  dies.  Duplex  or  Oster,  No.  3i,  l  inch  to  2  inches,  adjustable,  witli 

quiclv-opening  and  self-centering  dies  and  guides. 
1  set  of  dies  for  above  stock,  I  incli  to  2  iuclies. 
1  oil  can,  malleable  iron,  5  ounces. 
1  burring  reamer,  for  brace,  "  Lightning,"  1|  inches. 
1  pipe  former,  J  inch  to  1^  inches,  Vanderman,  No.  1. 
1  file,  half-round,  bastard,  6  inches. 
1  rasp,  smooth,  10  inches. 
1  tile,  hand,  smooth,  10  inches. 

POST      I'OOI,    <   IIKST. 

|Tht'  i)i)!<t  (oi)l  clii'sl    is  inatiiir:i(l  iircd  niHlcr  spci'itii'iil  ion  No.  .".'•O.I 

The  post  tool  chest  is  for  general  us(\  II  may  l»e  issikmI  to  coasl  defense 
artillery  engineers,  for  use  in  maintenance  of  fire-control  and  post-telephone 
systems.  The  ('(luipment  consists  of  tools  most  frequently  used  in  inuintainiug 
electrical  installations.     Figure  S-20  illusti-ates  the  post  tool  chest. 

Niiiiic    jtldlf. 

I'osr  'i'ooi,   CiiKsf. 

SicNAi,  ('oiii's,   r.    S.   Akmv. 

No.   . 

3  bite,  |§-inch,  ^"j-i"^^^  '^'^^^  ,''g-in(li,  Irwiu. 

T  brace,  ratchet,  ball-bearing,  8-in<li  throw,  Milleis  l-'alls  Co.,  No.  33. 
1   chisel,  socket,  3-i'i<h,  beveletl  edge,  .leiming.s,  No.  70. 
1  chisel,  cold,  J-inch. 

(348) 


Technical  Equipment  Issued  by  the  Signal  Corps. — Chapter  8.  67 


Fig.  8-20.— CHEST,  TOOL.    POST. 

1  file,  "  Arcade,"  with  handle,  6-inch  round,  bastard. 
1  file,  saw,  with  handle,  8-inch  D.  E.,  "  Arcade." 
1  file,  8-inch,  clear  edge,  "  Arcade,"  with  handle,  hand,  bastard. 
1  hammer,  claw,  "  Atha,"  No.  41*. 

1  holder,  tool,  Millers  Falls,  No.  5,  containing  the  following: 
1  4-inch  saw. 

1  8-inch  saw. 

2  screw  drivers. 
1  chisel. 

1  gouge. 

2  awls. 

1  gimlet. 

1  three-cornered  file. 

1  reamer. 
1  hatchet,  claw.  4J-incli  blade,  "Keen  Kutter,"  A.  C.  3. 
1  knife,  draw,  14-inch  blade.  "  Keen  Kutter,"  telegraph  pattern. 
1  oil  stone.  "  Pike."  soft,  Arkansas.  5  inches,  mounted. 
1  plane,  iron,  "Keen  Kutter,"  No.  4c. 

1  pliers,  pair,  6-inch  side-cutting,  U.  D.  F.  &  T.  Co..  No.  50,  or  P.  S.  &  W..  No.  40. 
1  rule,  2-foot,  fourfold,  boxwood,  brass  bound,  C.  S.  Co.,  No.  62^. 
1  saw,  20-inch,  crosscut.  9  Pts.,  Disston's. 
1  saw,  24-inch,  crosscut,  S  Pts.,  Disston's. 
1  screw  driver,  "  Perfect."  6-inch. 
1  sgnai'e,  graduated,  9-inch.  "  Stanley,"  No.  20. 


(349) 


68 


Signal  Corps  Manual  No.  3. — Chapter  8. 


1  tape,  metallic.  "  Lufkin."  50-foot.  No.  503. 

1  wrench,  screw:  10-inch  (opening  in  jaws  l\i  inches),  Coe's  or  Bemis  &  Call's, 
No.  54. 

SERVICE    TOOL    BAG. 

[The  service  tool  bag  is  manufactured  under  specification  No.  mi!.] 

The  service  tool  bag  is  constructed  of  fair  leather,  not  less  than  three  thirty- 
seconds  inch  in  thickness.  It  is  equipped  with  suitable  carrying  strap  and  lock. 
Cleats  for  holding  a  limited  number  of  tools  are  sewed  to  the  leather  on  inside 
of  back,  ami  consitlerable  room  for  small  miscellaneous  supplies  is  available 
within  the  bag.  ' 

The  service  tool  bag  is  issued  with  oi-  without  tools  and  may  be  furnished 
any  Signal  Corps  construction  jiarties.  It  is  also  issued  for  use  in  mainte- 
nance of  tire-control  and  post-telephone?  systems.  Figure  S-'21  illustrates  the 
service  tool  bag. 


Fig.  8-21.— BAG,   TOOL,   SERVICE. 


Fj  qui  1)111  vnl. 


1  try -.square,  steel.  4-inch  blade.  Stanley,  No.  12. 

I  chisel,  cold,  A-iucIi. 

1  chisel,  wood,  ^-inch  .socket  i)Iade.  iron,  ring-toi'pcd  handle,  .Icnning.s,  No.  15. 

1  hammer,  claw,  16-ounce,  Atha,  No.  41i. 

1  handle  with   tools.  No.  5,  MilhM-s  Falls  Co. 

1  knife,  Em])ire  Knife  Co.'s  No.  1013. 

1  level,  pocket,  spirit,  3-inch,  No.  31,  Stanley's. 

1  plane,  block,  Stanley,  6-inc'h,  No.  18. 

1  plier.s,  pair,  G-inch,  side  cutting,  U.  D.  F.  &  T.  Co.,  No.  50,  or  I'.  S.  iV:  W.,  No.  40. 

1  plier.s,  pair,  8-incli,  side  cutting,  U.  D.  F.  &  T.  (>>..  No.  50,  or  W  S.  iV  W.,  No.  40. 

14-foot  rule,  folding,  l)ox\vood,  8  parts.  Stanley,  No.  404. 

1  saw,  back,   lO-iridi,    Disston's. 


(360) 


Technical  Equipment  Issued  by  the  Signal  Corps. — Chapter  8. 


69 


1  screw  driver,  Terfect,  II.  D.  S.  Co.,  (i-incli. 

]  .screw  driver,  Perfect,  H.  I).  S.  Co.,  10-incli. 

1  solder,  resin  core,  pound. 

1  wrench,  screw,  Coe's  forged,  6-inch  monlcey  wrencii.  or  P.einis  &  Call's  No.  54. 

1  wrench,  socket,  for  telephone  apparatus,  4-inch. 

1  ratchet  hrace.  Millers  Falls,  S-inch  throw.  No.  33. 

1  i-inch. 

1  g-incli, 

1  ^-inch.  \  Irwin  aimer  bit.s. 

1  g-inch, 

1 1-inch. 

1  polarity  indicator,  M.  K.  S.  Co.,  No.  3321. 


I.NSPKCTOK  S    I'OCKKT     KIT. 

[The  Inspector's  pocket  kit  is  manufactured  under  specification  No.  186.1 

As  the  name  implies,  the  inspector's  pocket  kit  is  of  such  size  that  it  may 
he  conveniently  placed  in  a  pocket  of  clothing.  Tlie  tools  furnished  with  this 
kit  are  only  tho.v;e  which  may  l)e  required  for  tlie  repair  of  an  instrument  or 
inside  line. 


Fig.  &-22.— KIT,  TOOL,    INSPECTOR'S   POCKET. 
(351) 


70 


Signal  Corps  Manual  No.  3. — Chapter  8. 


The  case  is  made  of  leather  which  folds  in  such  a  manner  that  when  closed 
it  is  impossible  for  the  contents  to  become  dislodged  from  the  case.  The 
inspector's  pocket  kit  is  shown  in  figure  8-22. 

Marking. 

The  carrj-ing  case  has  stamped  into  the  leather  the  following: 

Inspector's  Pocket  Kit, 

U.  S.   Signal  Corps. 

No.  . 

Equipment. 

1  screw   driver    and    skinning   knife,    combined,    with    safety    spring,    Empire, 

No.  372. 
1  scissors,  electrician's,  5-inch,  nickeled,  J.  Wiss  &  Sons. 
1  pliers,  5-inch,  side  cutting,   nickeled,  pair,  U.  D.  F.  &  T.  Co.,  No.  12.50,  or 

P.  S.  &  W.,  No.  1240. 
1  file,  bastard,  3-inch,  half  round,  with  handle 
1  tweezers,  4i-inch,  nickeled,  pair. 
1  screw  driver,  2-inch,  Tuck's  Giant. 
1  rule,  2-foot,  narrow,  fourfold,  boxwood,  brass  bound.  C.  S.  Co.,  No.  02*. 

Electric  drills,  spring  hammers,  and  other  special  tools  are  kept  in  stock 
at  Signal  Corps  general  supply  depots,  and  are  issued  to  construction  parties 
when  the  magnitude  of  the  work  involved  warrants  such  action.  These  special 
tools  should  be  invariably  returned  to  supply  depot  from  which  received,  upon 
completion  of  the  work  for  which  they  are  issued,  unless  instructions  for 
different  action  are  issued  by  the  Chief  Signal  Officer  of  the  Army. 

MOLDINGS. 

Three  types  of  wooden  molding  are  supplied  by  the  Signal  Corps  where  it  is 
desired  to  conceal  inside  wiring  by  this  means.  The  sizes  of  these  three  types, 
winch  are  designated  A,  B,  and  C,  respectively,  are  shown  in  figure  8-23. 


TYPE  -A 


TYPE  -  B 


Fig.  8-23.  — MOLDING,    STANDARD    TYPES. 


(:i52) 


Technical  Equipment  Issued  by  the  Signal  Corps. — Chapter  8.  71 

GROUND   KOUS. 

Three  types  of  ground  rods  are  now  issued  l)y  the  Signal  Corps,  type  A,  type 
D,  and  type  K.  Otlier  types  liave  been  issued  in  tlie  past  but  are  now  considered 
obsolete.  Tlie  type  A  ground  rod  consi.sts  of  a  f  inch  by  5  feet  heavily  gal- 
vanized iron  rod,  pointed  at  one  end  and  equipped  at  other  end  with  a  short 
piece  of  C(tpper  wire,  soldered  to  the  rod.  They  are  supplied  for  making  gi'ound 
connections  for  post  telephone  .systems  employing  aerial  line  construction  where 
it  is  impi-acticable  to  connect  to  a  water  pipe  or  wherever  it  is  desired  to  estab- 
lish a  iicrmanent  groiuul  connection.  Where  ground  connecticms  are  obtained  by 
attachment  to  water  pipes,  suitai)le  clamps  for  the  purpose  are  furnished. 

The  tyi>e  D  ground  rod  is  9  inches  in  length,  made  of  hexagonal  .steel  one- 
fourth  inch  diameter  (across  flats),  pointed  at  one  end  and  bent  into  circu- 
lar form  at  the  other.  The  circular  end  is  equipped  with  a  machine  screw  for 
connection.  This  ground  rod  is  i^sed  almost  exclusively  for  making  gi-ound 
(•(innection  for  the  service  buzzer  and  forms  a  part  of  the  "ground  rod  and 
connector"  which  is  furnished  as  a  part  of  the  service  buzzei*. 

The  type  E  ground  rod  consists  of  a  round  galvanized  iron  rod  24  inches  long, 
liolnted  at  one  end  and  equipped  with  a  loose  iron  ring  at  other.  The  rod  is 
slightly  flattened  appi'oximately  three-fourths  inch  below  where  ring  is  at- 
tached and  a  machine  screw  for  making  line  connection  is  threaded  through 
the  rod.  The  loose  ring  is  used  for  withdrawing  the  ground  rod.  This  type  is 
for  use  in  connection  with  cam])  telephone  systems  or  wherever  a  temporary  or 
semipermanent  ground  connection  Is  desired. 

KNIFE    SWITCHES. 

Knife  switches  of  various  types  and  sizes  are  furnished  upon  receipt  of 
requisition,  when  approved  by  the  Chief  Signal  Officer  of  the  Army. 

MOOri.   PAINT. 

This  paint  is  similar  to  black  asphaltum  paint,  and  is  used  on  the  exterior  of 
conduits,  junction  boxes,  and  other  surfaces  exposed  to  the  weather.  Storage 
battery  stands,  when  constructed,  should  be  given  at  least  two  coats  of  this 
paint. 

SOLDER. 

Resin  core  solder  consists  of  a  round  wire  of  solder,  with  aperture  through 
center  filled  with  powdered  resin,  q'lie  resin  acts  as  a  flux,  and  no  injurious 
effects  result  from  its  use.  Resin-core  solder  should  always  be  used  in  solder- 
ing splices  and  connections  where  small  wire  is  involved. 

H(ilf-(ni(t-JifiIf  solder  is  supplied  for  soldering  on  lugs  and  similar  work. 

Plumbers'  solder  is  supplied  for  wiping  joints. 

BBIDLE    KINGS. 

Bridle  rings  of  various  sizes  are  furnished  for  supporting  bridle  wires  be- 
tween aerial  lines  and  cable  pole  boxes.  They  are  also  used  where  it  is  desired 
to  support  one  or  more  twisted  pair  wires  for  a  considerable  distance  along  the 
side  or  under  the  cornice  of  a  building. 

The  approved  bridle  ring  is  of  iron,  coated  with  enamel.  Figure  8-24  illus- 
trates the  bridle  ring. 


(353) 


72  Signal  Corps  Manual  No.  3. — Chapter  8. 

Fig.  8-24— RINGS,    BRIDLE.    ENAMEL  COATED. 
I'HOTOGKAIMIY. 

For  service  in  the  field,  where  :i  plioto.uraphic  outfit  is  required,  the  Signal 
Corps  will  supply  a  high-grade  camera  and  holders,  of  a  type  intended  for  the 
use  of  film  packs  or  film  rolls,  and  taking  a  picture  SI  by  4^  inches.  Film  packs 
or  rolls  will  also  be  supplied,  but  no  developing  or  printing  equipment  will  be 
furnished  with  them  except  under  special  circumstances.  ^Yhen  all  the  films  in 
the  pack  or  roll  have  been  exposeil  they  should  be  put  in  strong  opaque  wrapper 
and  mailed  immediately  to  the  Chief  Signal  Officer  of  the  Army,  stating  that  they 
are  exposed  films  to  be  developed  and  inclosing  a  statement  of  the  subjects. 
These  will  be  developed  in  the  signal  office,  Wasiiington,  by  an  expert  photog- 
rapher, and  the  person  sending  them  will  be  furnished  one  unmounted  print 
of  each,  enlarged  or  of  size  of  negative.  Pictures  which  are  of  special  interest 
and  value  will  be  enlarged  from  tlie  negatives  to  S!  by  10  size  and  plac<»d  in 
the  oflicial  album. 

All  photographic  negatives  (»f  instruments.  e(piiiimen(.  etc..  known  as  "techni- 
cal negatives,"  will  be  filed  in  the  ollice  of  the  Cliief  Signal  Officer  of  the  Army. 

When  forwarding  photographic  pi-ints  to  the  office  of  the  Chief  Signal  Officer 
of  the  Army  for  file,  they  should  be  sent,  as  far  as  practicable,  unmounted. 

It  is  not  intended  tliat  iiliotograiili  ]>la(cs.  fihus,  choinicals,  or  other  materials 
liable  to  deterioration  )k'  kept  in  sfock  at  general  supply  dei)ots  of  tlie  Signal 
Corps. 

SCKKW    ANCIIOItS.    , 

Screw  anchors  are  used  where  it  is  dcsii-cd  to  C.-isicn  tclcpliones,  other  appa- 
ratus, conduit,  etc.,  to  walls  of  conci-i'lt"  or  brick.  In  using  these  anchors  it  is 
,nH-essary  to  first  drill  a  hole  of  correct  dianu'ter  j)y  means  of  drills  furnished 
with  tool  kits.  After  hole  has  been  drilled  proper  depth,  the  screw  anchor  is 
insertt'd  and  wood  screw  or  lag  screw  of  proiier  dimensions  is  screwed  into  the 
intei'ior  of  the  anchor.  The  anchor  is  of  such  shape  that  as  the  wood  screw 
passes  into  the  anclioi-  Ibe  lalfei-  is  (>xpande(l. 


.^opSc/etv      ^FH  \\codJcreiY  H  H. Wood  Screw 


Composition 


Fig.  8-25.— ANCHORS,   SCREW.   COMPOSITION. 

(:!r.4i 


Technical  Equipment  Issued  by  the  Signal  Corps. — Chapter  8.  73 

The  strength  of  Ihcsc  mikIuh's  is  jmiiilc  for  use  in  ihe  iiistallalion  of  telei)liones 
and  siniihir  lifiiil  aiti)ai'alus.  It  iiiusi  he  uihIci-s|<mm|,  liowevcr,  that  tlie  holding 
IMiwcr  of  Ihciii  is  liiiiilcd  to  the  strcnglii  of  thread  in  tiie  lead  or  composition, 
consequently  liu-y  are  not  as  strong  as  a  lag  holt  properly  cemented  into  the  wall. 

The  holes  drilled  for  the  anchor  should  he  ahout  one-fourth  inch  deeper  than 
the  length  of  the  anchor  and  of  such  size  as  to  provide  an  easy  driving 
fit.  Great  care  should  be  exercised  in  installing  the  anchor  in  order  to  iirevent 
the  screw  from  passing  entirely  through,  therehy  coming  in  contact  with  bottom 
of  the  liole  in  wall.  The  anchors  are  furnished  in  various  sizes,  those  most 
conunonly  used  being  for  Nos.  1(»,  11.  oi-  \1  wood  screws,  and  for  a  three-eighths- 
incli  lag  screw. 

77/c  cutter  toijfilc  is  siipi)lied  for  use  in  the  installation  of  conduit,  cables,  etc., 
on  tiled  walls.  It  has  been  found  to  t)e  a  very  satisfactory  device  for  the  in- 
stallation of  signal  and  similar  appaialus  on  wails  which  are  lined  with  tiling. 

SWITCIIItOARDS. 

Switchboards : 
Telegraph — 
2-line. 
S-Mne. 

.lacks,  spring, 
rings— 

With  cord,  for  Jack  si)ring. 
Switchboard,  post  telephone,  common  battery: 

nO-line,  visual  signals,   fully  e(iui))jied  ami  complete  with  arrester  cabinet. 
KKI-line,  visual  signals,  fully  e(nii]i]K'(l  and  comjjlete  with  arrester  cabinet. 
l(»(»-line,  lamp  signals,  fully  (-(luipiied  nnd  complete  with  ;M-rester  cabinet. 
2(K)-line,  lamp  signals,  fully  (H|uiiiiied  and  complete  with  arrester  cabinet. 
300-line,  himp  signals,  fully  ecpiipped  ;ind  complete  with  arrester  cabinet. 
GOO-line,  lamp  signals,  multiple,  fully  ('(piipped  and  complete  with  arrester 

cabinet. 
Repair  parts  for — 
Bell,  night. 
Buzzer,  complete. 
Cabinet  arrester — 

For  50-line  common  battery  switchboard. 
For  100-line  common  battery  switchboard. 
For  200-line  common  battery  switchbo;u-d. 
Repair  parts  for — 

IJne  terminal,  strips  of  ]0  jiair. 
Protector — 

Carbon,  pairs  for. 

Complete,   in   strips  of  number   of  pairs   recpiired,    W.   E. 

No.  84. 
Heat  coils,  for. 
Micas  for 
Strips,  wood — 

For  mounting  line  terminals  (give  length  of  strip). 
For  m()unting  protector  (give  length  of  strip). 
Coils,  impedence  or  retardation,  for  operator's  set. 


(355) 


74  Signal  Corps  Manual  No.  3. — Chapter  8. 

Switchboard,  post  telephone,  common  battery — Continued. 
Condenser — 

1-microfarad,  cord  circuit. 
2-microfarad,  for  magneto  line. 

2-microfarad,    for    operator's    set    (for    either    primary    or    secondary 
circuit). 
Cord,  connecting — 

2  or  3  conductor  (give  length  of  cord  and  style  of  terminals)— 
2-conductor,  72-inch. 
3-conductor,  72-inch. 
Fuses — 

Baby,  5-ampere. 
Mica,  1-anipere. 
Generator^ 
Complete. 
Crank  for. 
Handle,  hard  rubber,  for  ringing  and  listening  keys. 
Induction  coil  for  operator's  set. 
Jack,  line — 

Common  battery,  cduiplele  (single  or  in  strips  of  10). 
Magneto,  coinplete. 
Jack,  operator. 
Key — 

Night  bell. 

Kinging  and  listening. 
Lamp — 
Pilot— 

24  or  30  volt. 
Cap  for. 
Socket  for. 
Supervisory — 
24  or  30  volt. 
Cap  for. 
Socket  for. 
Plug— 

For  connecting  cord. 
Operator. 
Receiver — 
Cap  for. 
Cord  for  (give  length  and  style  of  terminals)  — 

Cord,  72-inch,  no  plugs,  2-i)iii  and  2-\vasher  terminals,  for. 
Diaphragm  for  (give  diameter). 
Single  head. 
Relay — 
Cord — 

Complete. 
Coils  for. 
Pilot 

('oil   for. 


(.•?56) 


Technical  Equipment  Issued  by  the  Signal  Corps. — Chapter  8.  75 

Switchboard,  post  telephone,  common  battery — Continued. 
Relay — Continued. 
Signal — 
Line — 

Common  battery,  complete. 
Coil  for  common  battery. 
Magneto,  complete  with   nittimting. 
Magneto,  coil  for 
Supervisory — 
Coil   for. 

Complete  with  UKiunting. 
Terminals — 
Cord,  shelf. 
Lint". 
Transmitter — 
Comi)lete. 
Cords  lor  (give  length,  style  of  terminals,  and  state  whether  1  or 

2  conductor). 
Mouthpiece  for. 

Note. — In  requesting  repair  parts  of  switchboards  and   pro- 
tector cabinet,   give  manufacturer's   name,   type,   and,   if  prac- 
ticable, Signal  Corps  serial  or  order  number. 
Switchboard,  post  telephone,   local   battery,    IHO-line. 
Switchboard.  i)ost  telephone,   L.   K.,  r>()-drop. 
Bell,  night. 

Bell,  night,  switch  for. 
Cabinet,  arrester,  50-line. 
Coil,  induction,  operator's. 
Cord,  connecting    (72-inch),  without  plugs. 
Generator,  hand. 
Generator,  hand,  crank  for. 
Jacks,  line,  complete. 
Key,  ringing  and  listening,  complete. 
Plug,  for  connecting  cord. 
Receiver,  single  head — 
Complete. 

Cord  for,  without  plug. 
Diaphragm  for. 
Signals,  line — 
Complete. 
Coils  for. 
Signal,  supervisory — 
Complete. 
Coils  for. 
Transmitter — 
Complete. 
Cord  for. 
Mouthpiece  for. 


(357) 


76  Signal  Corps  Manual  No.  3. — Chapter  8. 

Switchboards,  niiscelljineoiis : 

20-line,  telephone,  portable,  niauneto  tyi)e. 
Power — 

Complete,  for  use  with   motor  generator. 
Type  2. 
Type  4. 

With  (listrilmtini;-  frame,  for  tire-eontrol  swilchboui-d  room. 
Frame,  (li.stributin.ii,   tor. 
Switchboards,  telephone,  chargini;-  panel,  types  1   to  5: 
Type  1. 
Type  2. 
Type  5. 

(In  requesting  repair  parts  for  any  of  the  instruments  mounted  on 
this  board,  the  data  shown  on  name  plate  of  that  particular  instrument 
shouhl  be  entered.) 

<A.\n>    TKKEl'HOXK    SWITCHHOARl). 

This  portable  telephone  switchboard  was  desiuned  by  the  Signal  Corps  and 
is  the  result  of  a  development  which  has  been  in  process  a  nmnber  of  years. 
It  is  installed  at  camps  in  connection  with  administration  telephone  systems 
and  has  a  capacity  of  40  lines. 

The  ca.se  whicli  contains  the  switchboard  jtroper  is  of  basswood,  lined  inside 
and  out  with  tiber.  All  of  the  conii)onent  parts  of  the  switchboard  proper  are 
moiuited  upon  an  iron  frame,  which  may  be  withdrawn  from  case  by  removing 
four  screws.  When  this  switchboard  is  set  up  for  oi)eration,  it  is  supi»orted  by 
f(»ur  legs,  which  are  tele.scoi)ic  and  consequently  ad.ju.stable.  l>y  an  oitening  in 
the  bottom,  the  cord  weights  and  cords  are  allowed  to  protrude  through  bot- 
tom, assmning  the  usual  ])osition  of  the  coi'ds  of  the  ordinary  conunercial 
switchboard.  The  rear  of  the  switchboard  case  is  hinged,  and  when  opened 
access  may  lie  had  to  a  vei\v  compact  form  of  telei)hone-line  ])rotectors.  Lines 
may  lie  very  (juickly  coiniected  to  tlu'se  protectors,  as  each  comiection  is  made 
by  means  of  a  Fahnestock  clip,  it  being  merely  necessary  to  depress  a  spring, 
insert  wire,  and  relea.se  spring  to  make  connection.  Each  protector  consists  of 
two  carbon  blocks  and  dielectric  and  a  suitai)l(>  fuse,  all  of  whii-li  is  considered 
an  efficient   telephone-line  ])rotector. 

On  tiic  front  of  the  switchboard  is  mounted  a  clock.  No  key  is  required  to 
wind  it.  it  being  merely  necessary  to  revolve  a  disk  in  order  to  wind.  The 
Ir.Miismitter  is  of  suspended  type  and  is  suiiiiorted  by  a  mtMal  arm  which  folds 
back  and  locks  when  the  switchboard  is  not   in  use. 

When  this  switchbo.-ird  is  iJi-ejiai-ed  lor  1ransi)ortation  or  for  sti>rage,  the 
legs  which  su])port  the  switchboard  are  ti'lescoped  to  their  shortest  length 
and  ai"e  placed  in  rear  of  case,  suitable  mooring  for  them  being  provided 
therein.  The  upiu-r  part  of  the  case,  which  is  detachabli>,  is  jdacivl  into  position 
and  fastened.  The  cord  weights  and  cords  are  jtlaced  in  a  <'onq)ai"tment  pro- 
vided for  that  puri)ose.  ;iihI  the  switchboard  closely  res«Mnl)les  a  small  chest. 
The  accoiiqianying  illustration  shows  the  switchboard  ready  for  ()peratlon  and 
ready   lor  (ransjMirtat  ion  or  storage. 


(358) 


Technical  Equipment  Issued  by  the  Signal  Corps. — Chapter  8.  77 


Fig.  8-26.— SWITCHBOARD,   CAMP    TELEPHONE. 


Part 

No. 


Name. 


Case  complete 

Case,  handle  for 

Case,  name  plate 

Case,  Irimk  catch  for 

Case,  rear  cover,  complete 

Case,  rear  cover,  hinge  for 

Case,  front  cover  for 

Case,  les  socket  for 

T^eg,  telescopic 

l>eg,  telescopic,  upper  section 

Leg,  telescopic, lower  sect  ion 

l/cg,  telescopic, clamp  complete 

l/Cg, telescopic, clampscrcw  for 

Leg,  telescopic,  wing  nut  and  screw. 

Single  head  receiver 

Single  head  receiver,  headband  for. . 

Single  head  receiver,  cord  for 

Receiver,  cap  for 

Transmitter  bracket  complete 

Transmitter  bracket,  catch  for 

Transmitter  bracket,  hinge  for 

Transmiltcr  complete 

Transmit t er,  cap  for 

Transmit  t  er ,  cord  for 

Clock. 


Reference 

No. 


Line  signals  and  moimting  (strips  of  10),  give  numbers. .. 

Line  signal  coil 

Line  signal  shutter 

Line  jack  and  mounting  (strips  of  10),  give  numbers 

Receiver  jack  ( 1 ) 

Receiver  j ack  plug 

Transmit  t  er  jack  ( 1 ) 

Transmit  t  er  jack  plug 

Kev,  night  alarm 

Key,  night  alarm,  handle  for 

Key,  ringing  complete 


(Continued  on  next  page.) 
(350) 


31 


78 


Signal  Corps  Mcinual  No.  3. — Chapter  8= 
(Parts  list— Continued.) 


Part 
No. 


Name. 


Reference 
No. 


Key,  ringing,  handle  for 

Key,  ringing  and  listening 

Key,  ringing  and  listening,  handle  for. 

Cord,  connecting 

Cord,  connecting  plug  complete 

Cord,  connecting,  weight 

Tool  kit  complete 

Tool  kit,  snipe  nose  pliers 

Tool  kit ,  diagonal  pliers 

Tool  kit,  screw  driver,  large 

Tool  kit ,  screw  driver,  small 

Tool  kit ,  wrench 

Tool  kit ,  case  for 

Magnet  o  complete 

Magnet  o,  crank  handle 

Magnet  o ,  gear 

Magneto,  pinion 

Magneto,  contacts 

Magneto,  armature 

Lightning  arrester  complete 

Fahens t  ock  clip 

Carbons  and  dielectrics 

Fuses,  line 

B  uzzer,  ringing 

Battery  (2  No.  6  dry  cells  per  set) 


33 
34 
35 
36 
37 
38 
39 
40 
41 
42 


TELEPHONES. 

Wall,  common  battery   (uulo  pay  station). 

Field. 

Common   battery : 

Desli  set,  complete. 
Repair  parts  for — 
Bell  set,  complete. 
Binding  posts,  locknut. 
Condenser,  2-microfarad,  complete. 
Cord,  main  (state  whether  2  or  3  conductor). 
Cord,  receiver. 
Desk  stand,  complete. 
Induction  coil,  complete, 
lieceivei- — 
Cap  for. 

Diaidn-agiii   for    (give  diaiiieler). 
lliiiid,  coinplclt'. 
Sliell   lor. 
Ringer — 

Coils  for. 

('onipleic  Willi  g(»iig.s. 
(Jongs  for. 
Transmit  I  or — 

( 'nniplclr. 
Kmicklc  joinl    lor. 
Mouthpiece  for. 
Wall  set,  complete,  wooden  case. 
Wall  set,  metal  case. 
Repair  parts  for — 

Binding  posts,  lockiuit. 
(!oil,    induction,    complete. 
Condenser,  2-microfa»ad,  complete. 
(360) 


Technical  Equipment  Issued  by  the  Signal  Corps. — Chapter  8.  79 


Common  battery  telephones. 

Wall  set,  metal  case — Continued. 
Repair  parts  for — Continued. 
Hook,  switch — 

Complete,  hut  without  hook  lever. 
Hook  lever  for. 
Receiver,  hand — 
Cap  for. 
Complete. 
Cord  for. 

Diaphragni  for   {fiivr  diameter). 
Shell  for. 
Ringer — 

Coils  for. 

Complete,  with  gong. 
Gongs  for. 
Transmitter — 
Complete. 
Arm  and  base. 
Mouthpiece  for. 
Telephone,  local  battery  : 
Desk  set,  complete. 

Repair  parts  for — 

Bell  sets,  complete. 
Binding  posts,  locknut. 
Cord  for  receiver. 

Cord,  main  (state  whether  3  or  4  conductor), 
Desk  stand,  complete. 
Generator — 
Complete. 
Handle  for. 
Induction  coil,  complete. 
Receiver,  hand — 
Cap  for. 
Complete. 

Diaphragm  for   (give  diameter). 
Shell  for. 
Ringer — 

Coils  for. 

Complete,  with  gongs. 
Gongs  for. 
Transmitter — 
Complete. 

Heads  (knuckle  joint). 
Mouthpiece  for. 
^^"all  siM.  complete. 

Repair  parts  for — 

Binding  posts,  locknut. 
Hook  switch — • 

Complete,  but  without  hook  lever. 
Lever  for. 
Induction  coil,  complete. 


(361) 


80  Signal  Corps  Manual  No.  3. — Chapter  8. 


Local  battery  telephones: 

Wall  set,  complete — Continued. 
Repair  parts  for — Continued. 
Magneto  generator — 
Complete. 
Crank  for. 
Receiver,  hand — 
Cap  for. 
Complete. 
Cord  for. 

niaphragm  for  (give  diameter), 
t^hell  for. 
Ringer — 

Coils  for. 

Complete,  with  gongs. 
Gongs  for. 
•  Tran.smitter — 

Arm  and  base. 
Complete. 
Mouthpiece  for. 
Common  battery,  fire  control   (metal  case)  : 
Gun,  C.  B.  F.  C. 
Hand  set. 
Head  set. 

Plotter's  set,  C.  B.  F.  C. 
Wall,  C.  B.  F.  C. 
Battery  commander's,  C.  B.  F.  C. 
Camp : 

Maintenance  parts — 
Hand  set,  complete. 
Kinger. 
Generator. 
Cord,  for  hand   set. 
Field  (now  issued  for  target  ranges  oiilyi.  in.iinltMiauce  parts; 
Blocks,  hard  rubber — 
Receiver  ternunal. 
TransmitttM"  tenuinnl. 
Cases,  wtMid. 

Clips,  Itrass,   inductinii  coil   ifrmiiuu. 
Coii.s — 

Induction. 
Receiver. 
Ringer,  ."lOO-ohm. 
Cords,  telephone,  connector, 
('orners,  metal. 

Cover,  generator  crank  opeiuiig. 
Cranks,  generator, 
♦"'ups,  electrode,  complete. 
Diagram,    wiring. 
Diaphragm — 
Receiver. 
Transmitter. 
Disks,  mica,  transmitter. 

(302) 


Technical  Equipment  Issued  by  the  Signal  Corps. — Chapter  8. 


SI 


Fit'ld  telephone  (now  issued  for  target  ranges  only),  maintenance  parts — Contd. 
Fastener  for  cover. 
Gasket,  soft  rubber — 

Switch  opening. 

Transmitter  diaphragm. 
Generators,  3-l)ar,  with  cranks. 
Gongs,  bell,  with  screws  and  brackets. 
Hand   sets. 
Hinges,  strap. 
Post,  binding — 

Line. 

Lock  nut. 

Receiver  terminal. 

Transmitter   term i tin  1. 

Wing  nut. 
Ringer,  l,0()0-ohm. 
Rings,  swivel,  and  jilates. 
Shells,  liard  rubber,  for  liand  receivers. 
Springs — 

Switch,  with  platinum  contact. 

Transmitter,   dampening. 
Strni)s.  carrying,  black  leather,  complete  with  buckles  and  rings. 
Terminals,  coil. 

WIRE. 

A  great  percentage  of  all  wire  purchased  by  the  Signal  Corps  is  manufac- 
tured in  accordance  with  Signal  Corps  specifications  and  is  thoroughly  tested 
by  a  competent  inspector  before  being  accepted. 

DESIGXATIOX   OF   WIUE    IX    MILS. 

Hereafter  in  all  specifications,  purchase  orders,  contracts,  requisitions,  and 
other  communications  concerning  the  purchase,  inspection,  and  issue  of  all 
types  of  solid  wires  by  the  Signal  Corps,  reference  will  be  made  to  the  sizes  of 
wires  by  stating  the  diameter  in  thousandths  of  an  inch  (mils)  in  accordance 
with  the  table  of  mils  shown  below. 


1 

2 

3 

1 

2 

3 

1 

2 

3 

1 

2 

3 

Mils. 

B.W.G. 

B.&S. 

Mils. 

B.W.G. 

B.&S. 

Mils. 

B.W.G. 

B.&S. 

Mils. 

B.W.G. 

B.&S: 

460 
410 

365 

325 
289 
258 
229 
204 

182 

162 
144 

0000 
000 

00 

Oandl 
2 
3 

4  and  5 
6 

7 

8 
9 

0000 
000 

00 

0 

1 

2 
3 
4 

5 

6 

128 
114 

102 

91 
81 
72 
64 
57 

51 

45 
40 

10 
12 

13 
14 
15 
16 
17 

18 

i9 

8 
9 

10 

11 
12 
13 
14 
15 

16 

17 
18 

36 
32 

28.5 

25.3 
22.6 
20.1 
17.9 
15.9 

14.2 

12.6 
11.3 

20 
21 

22 

23 

24 

25 

26 

27 

f        28 

{     and 

I       29 

30 

31 

19 

20 

21 

22 
23 
24 
25 
26 

}    '^ 

28 
29 

10.0 
8.9 

8.0 

7.1 
6.3 
5.6 
5.0 
4.5 

4.0 

3.5 
3.1 

33 
34 
35 
and 
36 
37 
38 

39' 

40 



30 
31 

1      32 

33 
34 
35 
36 
37 

38 

39 
40 

Note. — The    standard    sizos    in    mils    indicated    are    the    sizes    in    the    American    wi 
gauge  (B.  &  S.)  rounded  oflf  to  about  the  usual  limits  of  commercial  accuracy. 

(See  next  page.) 


4(mS1°— 17 24 


(.%.^) 


82  Signal  Corps  Manual  No.  3. — Chapter  8. 

The  table  shows  (column  1)  the  War  Department  standard  sizes,  diameter 
in  mils;  and  (column  2)  the  nearest  commercial  Birmingham  wire  gauge; 
and  (column  3)  Brown  &  Sharpe,  or  American  wire  gauge,  for  approximately 
the  same  size  wire. 

The  difference  between  successive  sizes  is  approximately  a  constant  per  cent 
of  the  size. 

The  following  wires  are  supplied  by  the  Signal  Corps  for  radio-telegraph  in- 
stallations only  and,  inasnmch  as  they  are  special  in  character,  will  not  be  de- 
scribed herein.  For  detailed  information  concerning  them.  Signal  Corps  specifi- 
cation No.  416  should  be  perused. 

High  tension   (one  size  only).  Antenna  cord  (one  size  only). 

Low  tension   (five  sizes).  Counterpoise   (one  size  only). 

Antenna   (two  sizes).  Silicon  bronze  (one  size  only). 

Wires  supplied  liy  the  Signal  Corps  in  connection  with  installation  of  fire- 
control  systems,  jiost-telephone  systems,  small-arms  target-range  signaling  sys- 
tems, and  lines  of  security  and  information  are  as  follows : 

Inside  twisted  pair   (one  size  only). 

Inside  twisted  triple  conductor  (one  size  only). 

House  (one  size  only). 

Pot  head  (one  size  only). 

Cross-connecting  (two  sizes  25.3  and  30  mils,  respectively). 

Rubber-covered   (various  sizes). 

Fixture  (two  sizes,  40  and  51  mils,  respectively). 

Weatherproof  (various  sizes). 

Bridle   (one  size  only). 

Outside  twisted  pair  (two  sizes,  64  and  81  mils,  respectively). 

Outside  distributing,  copper-clad   (one  size  only). 

Hard-drawn  copper  (various  sizes). 

Galvanized  iron  (various  sizes). 

Buzzer  (one  size  only). 

Field    (one  size  only). 

Office  (two  sizes,  36  and  51  mils,  respectively). 

A  brief  description  of  these  wires  in  the  order  listed  follows: 

INSIDE    TWISTED    PAIR. 

This  wire  consists  of  two  separately  insulated  conductors  twisted  together. 
Each  conductor  is  40  mils  diameter,  soft  cojipor,  and  is  insulated  with  rubber 
compound  and  cotton  braid.  The  braid  of  one  conductor  is  red  and  of  the  other 
black. 

This  wire  should  invariably  be  used  for  the  inside  wiring  of  fire-control 
stations,  and  may  be  used  for  inside  post-telephone  system  work  at  points  where 
wire  having  unusually  high  insulation  is  desired. 

INSIDE   TWISTED  TltlPI.E   COXDUrTOR. 

This  wire  consists  of  three  separately  iiisulated  conductors  twisted  together. 
Two  conductors  are  exactly  in  accordan<v  with  those  described  under  "  Wire, 
Inside  twisted  pair,"  iinmedlately  preceding.  The  third  conductor  is  also  similar 
except  that  it  is  supplied  with  a  yellow  braid. 

This  wire  is  used  in  fire-control  stations  where  the  head  or  hand  set  of  a  tele- 
phone is  used  at  some  distance  from  telephone  instrument  proper  and  connects 
the  telephone  with  telephone  terminal  block  lo  which  is  connected  the  head  or 

(364) 


Technical  Equipment  Issued  by  the  Signal  Corps. — Chapter  8.  83 

liiiiid  set.  It  is  also  used  between  telephones  proper  and  terniiiuil  boxes  in  tire- 
control  stations  when  it  is  desired  to  use  the  earth  as  one  side  of  the  rin^inj; 
(calling)  circuit.  It  may  also  l)e  used  in  connection  with  post  telephone  .systems 
where  a  triple  conductor  wire  having  unusually  high  insulation  is  desired. 


This  wire  consists  of  two  separately  insulated  conductors  twisted  together. 
Each  conductor  is  36  mils  diameter,  soft  copper,  and  is  insulated  with  rubber 
compound  and  cotton  braid.  Braids  of  conductors  are  furnished  in  various 
colors,  but  invariably  one  braid  contains  a  tracer  w-hich  consists  of  a  thread  of 
different  color  woven  in  the  braid. 

This  wire  should  be  used  for  inside  wiring  at  post  telephone  substations, 
except  substations  which  are  tire-control  stations. 

POT  HEAD. 

This  wire  consists  of  two  separately  insulated  conductors  twisted  together. 
Each  conductor  is  36  mils  diameter,  soft  copper,  and  is  insulated  with  rubber 
compound  only,  there  being  no  braid  supplied.  A  conductor  may  be  traced  by 
means  of  two  ridges  formed  of  the  rubber  compound  of  one  conductor. 

Formerly  pot-head  wire,  with  one  conductor  black  (natural  compound  color) 
and  the  other  red,  was  furnished.  The  colored  compound  becomes  porous  in  a 
comparatively  short  time ;  consequently  only  pot-head  wire  with  natural  color 
compound  should  be  used  under  any  circumstances  for  permanent  construction. 

Pot-head  wire  is  used  in  the  construction  of  pot  heads  of  all  paper-insulation 
cable  and  may  be  used  as  cross-connecting  wire  in  terminal  boxes. 

A  special  pot-head  wire  is  furnished  for  use  in  the  Tropics. 

CROSS    CONNECTING. 

This  wire  consists  of  two  separately  insulated  conductors  twisted  togetlier. 
Each  conductor  is  of  soft  copper,  insulated  with  rubber  compound  and  a  flame- 
proof cotton  braid.  It  is  a  commercial  product  and  replaces  the  large  wire  with 
yellow  and  black  braid  formerly  furnished  as  cross-connecting  wire. 

This  wire  should  ordinarily  be  used  for  cross  connecting  in  all  station  ter- 
minal boxes,  but  not  in  submarine  cable  terminal  boxes.  Cross  connecting  in 
submarine  cable  terminal  boxes  should  be  accomplished  with  fixture  wire, 
described  later. 

RUBBER  COVERED. 

This  wire  consists  of  a  single  soft-copper  conductor  insulated  with  rubber 
compound  and  cotton  braid  impregnated  with  a  waterproof  compound.  The 
sizes  of  the  conductors  most  commonly  used  are  64  mils  and  81  mils,  respec- 
tively. Any  commercial  size  of  conductor  can  be  furnished.  This  wire  is  used 
principally  in  fire-control  switchboard  rooms  for  power  leads  and  in  A\iro  forms 
for  power  switchboards ;  also  in  the  51-mil  size  for  wiring  to  apparatus  at 
butts  of  small-arms  target  ranges. 


This  wire  consists  of  a  single  soft-copper  conductor  insulated  with  a  thin 
wall  of  rubber  compound  and  a  cotton  braid  impregnated  with  waterproof  com- 
pound. It  is  furnished  in  two  sizes,  the  conductor  being  40  mils  or  .")!  mils 
diameter.  Fixture  wire  is  used  in  wire  forms  for  power  or  distril)uting  switch- 
boards and  in  cross  connectiiffe  in  submarine  cable  terminal  boxes. 

(365) 


84 


Signal  Corps  Manual  No.  3. — Chapter  8. 


WEATHERPROOF. 

This  wire  consists  of  a  single  hard-drawn  copper  conductor  insulated  with  a 
triple  cotton  braid  impregnated  with  a  waterproof  compound.  It  is  used  for 
extending  aerial  lines  through  the  foliage  of  trees.  It  is  also  used  in  wire 
forms  for  power  switchboards.  Weatherproof  wire  is  more  rigid  than  "  wire, 
rubber-covered,"  and  for  this  reason  only  is  it  preferable  for  wire  forms. 


This  wire  consists  of  a  single  soft-copper  wire  51  mils  in  diameter,  insulated 
with  rubber  compound  to  an  outside  diameter  of  five-thirty-seconds  inch,  and 
covered  with  a  closely  woven  braid  impregnated  with  a  weatherproof  com- 
pound. 

This  "wire  can  be  furnished  with  two  conductors,  twisted  together,  if  desired. 

Bridle  wire  is  used  for  connecting  aerial  lines  with  arresters  in  pole  boxes, 
or  wherever  a  51-mil  diameter  wire  with  heavy  insulation  is  necessary. 

It  differs  from  fixture  wire  in  tlmt  the  over-all  dimension  is  greater. 

OUTSIDE    TWISTED    PAIR. 

This  wire  consists  of  two  separately  insulated  conductors  twisted  together. 
Each  conductor  is  insulated  with  rubber  compound  am!  a  cotton  braid  impreg- 
nated with  moisture-proof  compound. 

Two  sizes  of  this  wire  have  been  furnished,  the  conductors  being  81  mils  and 
64  mils  in  diameter,  respectively. 

Outside  twisted  pair  is  useil  in  connecting  aerial  lines  witii  substations  and 
under  certain  conditions  it  may  be  used  as  aerial  line,  also  for  temporary  work 
of  viirious  characters. 

OUTSIDE  DISTRIBUTING,    COPPER    CLAD. 

This  wire  consists  of  two  separately  insulated  conductors  twisted  together. 
Each  conductor  consists  of  a  steel  core  upon  which  is  welded  a  copper  coat  of 
uniform  thickne.ss.  Each  conductor  is  4^  mils  diameter  and  is  insulated  witli 
rubber  compound  and  a  closely  woven  cotton  braid  impregnated  with  moisture- 
proof  compound. 

Outside  <listributing  copper-clad  wire  in  a  great  measure  supersedes  the  out- 
side twisted  pair  de.scribed  in  the  preceding  item,  it  is  smaller  and  lighter,  but 
used  for  the  same  purposes. 

HARD-DRAWN   COPPER. 

This  wire  consists  of  one  noninsulated  conductor  of  hard-drawn  copper.  It 
can  be  furnished  in  an.v  of  the  commercial  sizes,  but  smaller  than  81  mils 
diameter  should  not  be  used  for  permanent  lines.  The  81  mils  diameter  size  is 
suitable  for  practically  all  aerial  lines  constructed  by  the  Signal  Corps. 


Coppci 

line  icirc,  lianl 

Innni    (  hare). 

Weight 

Weight 

Resistance 

Resistance 

Tensile 
strength. 

Coil 
lengths. 

Diameter. 

per  1,000 
feet. 

per 
mile. 

perl  ,000 
feet  at  68°. 

per  mile 
at  68°. 

Mils. 

Pounds. 

PounJ.t. 

Ohms. 

Ohms. 

Pounds. 

Feet. 

182 

100 

529 

0. 323 

1.71 

l,,'j,')0 

1,000 

102 

79 

419 

.407 

2.15 

1,235 

1,000 

144 

03 

331 

.  Til  3 

2.71 

980 

2,040 

128 

'.JO 

2l'>2 

.(i40 

3.41 

778 

2,040 

114 

39 

208 

.815 

4.30 

017 

2, 040 

102 

32 

1(16 

1.028 

r,.  43 

489 

2,640 

91 

2T, 

132 

1 .  29(i 

0.S4 

388 

5,280 

SI 

20 

10,'i 

1.0.35 

8. 03 

307 

5,280 

72 

l.-).7 

83 

2.001 

10.88 

244 

6,280 

M 

12.4 

fi.") 

2.699 

13.  72 

193 

5,280 

(.".06} 


Technical  Equipment  Issued  by  the  Signal  Corps. — Chapter  8.  85 

i;A1,\  AMZKll     iltO.V. 

This  wire  consists  of  oni'  noniiisulated  coiKluctor  of  iron  wire,  lieavily  fral- 
vanized.  It  can  ho  furnislied  in  any  of  the  commercial  sizes,  hut  is  usually 
supplied  in  the  81  or  SO  mils  diameter  size  for  provisional  fire-control  or  post 
telephone  system  lines,  and  is  always  furnished  in  this  size  for  field  lance-pole 
lines ;  144  or  148  mils  diameter  size  is  usually  furnished  for  permanent  tele- 
graph "  lonji:  lines."  There  are  three  connuercial  grades  of  this  wire,  which 
are  designated  as  follows:  B,  BB,  and  EBB.  The  EBB  grade  Is  supplie<l  by 
the  Signal  Corps  unless  tensile  strength  is  more  important  tlian  conductivity 
for  a  given  size. 

In  connection  witli  tire  control  and  post  telephone  systems,  g-.dvanized-iron 
wire  should  be  used  for  aerial  lines  for  piT)visional  or  temporary  installation 
only. 

Galvanised-iron  wire. 


Diame- 

Area. 

■Weight 

per  1 ,000 

feet. 

Weight 

Breaking 

Resist- 
ance per 

Length 

ter. 

per  inile. 

strength. 

mile  at 
68°  F. 

of  coil. 

Mih. 

dr.  mils. 

Pounds. 

Pounds. 

Pounds. 

Ohms. 

Feet. 

2S9 

83, 521 

219 

1, 160 

3,480 

4.05 

1,000 

258 

66, 564 

175 

920 

2,760 

5.08 

1,000 

229 

52,  441 

138 

726 

2,178 

6.44 

1,000 

204 

41,616 

108 

576 

1,728 

8.12 

1,320 

1S2 

3.3, 124 

87 

458 

1,424 

10.19 

2;  000 

162 

26,  244 

69 

363 

1,089 

12.87 

2,000 

144 

20,736 

54 

287 

861 

16.28 

2, 640 

128 

16. 384 

43 

227 

681 

21.21 

2,640 

114 

12,996 

34 

179 

537 

25.98 

2,640 

102 

10,404 

27 

144 

432 

32.46 

2,640 

91 

8, 281 

22 

115 

345 

40.80 

2,640 

81 

6,561 

17 

91 

271 

51.56 

2,640 

This  wire  consists  of  a  single  insulated  conductor  composed  of  two  steel  and 
one  soft  copper  wires,  each  having  a  diameter  of  12  mils  before  tinning.  The 
insulation  consists  of  a  doul)le  wrap  of  cotton  impregnated  with  an  insulating 
compound.  The  finished  wire  has  a  diameter  between  0.0.35  and  0.004  inch,  iind 
is  furnished  by  manufacturers  on  metal  spools  which  contain  one-half  mile  of 
the  wire.  Buzzer  wire  is  used  exclusively  in  the  field  in  hurriedly  establishing 
communication  with  a  given  location.  If  practicable  it  should  be  recovered 
when  it  lias  served  its  purpose. 

FIELD. 

Field  wire  is  a  single  insulated  conductor  made  up  of  10  steel  wires  and  1 
soft  copper  wire.  The  copper  wire  is  28.;")  niils  diameter  and  each  of  tlie  steel 
wires  12  mils  diameter  before  tinning,  diameter  of  conductor  54  mils. 

The  conductor  is  insulated  as  follows :  First,  with  a  serving  of  cotton,  then 
a  seamless  rubber  compound  having  a  thickness  of  0.024  inch.  Tlie  rubber- 
covered  wire  is  then  covered  with  a  smooth,  closely-woven  braid  of  cotton, 
saturated  with  a  moisture  repellent  compound  and  given  a  wax  polish  finish.  It 
is  furnished  in  half-mile  lengths  on  small  wooden  reel.s. 

Field  wire  is  used  exclusively  in  the  field  in  hurriedly  establishing  communi- 
cation with  a  given  location  and  is  usually  paid  out  from  a  wire  cart  designed 
for  the  purpose.  It  is  also  used  in  semipermanent  linework  where  it  may  be 
supported  by  means  of  lance  poles. 

/S'p/ir/j!/;  field  tcire. — When  field  wire  has  been  broken  or  cut.  it  will  neces- 
sarily have  to  be  spliced.     Splices  in  field  wires  may  be  either  temporary  or 

(367) 


86  Signal  Corps  Manual  No.  3. — Chapter  8. 

permanent  in  character.  If  the  wire  is  severed  while  in  use,  the  lineman  should 
locate  the  fault  and  complete  the  splice  as  quickly  as  possible.  A  temporary 
splice  may  be  made  as  follows :  The  two  ends  of  the  severed  wire  having  been 
cauglit  up  the  ends  are  scraped  of  insulation  (skinned)  after  a  square  knot  has 
first  been  tied  by  knotting  the  two  ends  of  the  wire  together.  This  knot  is  made 
to  take  the  strain  off  of  the  splice.  Care  in  making  the  square  knot  should  be 
observed,  so  that  a  granny  knot  may  not  result.  After  knotting  the  wire  the 
skinned  ends  are  then  twisted  tightly  together. 

As  soon  as  convenient  the  wire  should  be  gone  over,  the  bad  lengths  cut  out, 
and  permanent  splices  made  in  place  of  the  temporary  ones.  To  make  a  per- 
manent splice,  skin  off  the  insulation  for  about  4  inches  on  each  end  and  sepa- 
rate the  steel  and  copper  strands,  so  that  the  two  copper  strands  may  first  be 
wound  tightly  together.  The  copper  may  be  distinguished  from  the  steel  by 
its  greater  pliability.  The  steel  strands  are  now  wound  together,  making  the 
joint  mechanically  secure.  Snap  off  the  loose  ends  and  solder  the  joint.  Wind 
insulating  tape  tightly  over  the  splice. 


This  wire  has  a  single  soft  copper  conductor  of  either  36  or  51  mils  diameter, 
insulated  with  a  vulcanized  rubber  compound,  covered  with  a  close-filled 
polished  cotton  braid,  and  is  furnished  in  500-foot  coils.  It  is  used  principally 
for  inside  wiring  in  connecting  up  telegraph  instruments,  electrc  bells,  etc. 

MISCELLANEOUS  WIKES. 

In  connection  with  making  electrical  measurements  and  for  various  pur- 
poses, the  following  wires  are  supplied  under  special  approval : 

Magnet ;  specify  mils  in  diameter,  supplied  in  single  or  double  cotton  or 

silk  insulation. 
Resistance ;  finished  as  follows — 

Single  cotton  covered. 

Double  cotton   covered. 

Single  silk  covered. 

Double  silk  covered. 

Bare. 
Silicon,  bronze,  bare,  28.5  mils  in  diameter ;  supplied  in  ^-mile  spools. 
German-silver,  30  per  cent  alloy;  see  note  under  table  below. 
Climax ;  see  note  under  table  below. 
S.  B.,  bare,   32.6  mils  in  diameter    (Driver-Harris). 
(Jernian-silver,  18  per  cent  alloy;  see  table  below. 

To  secure  uniformity  in  units  relative  to  i)(>nis  of  wire,  llu>  following  will  be 
observed : 

All  galvanized  iron  wire  to  be  in  miles.  (Fractions  less  lliaii  a  half  mile  may 
be  disregarded.) 

All  bare  copper  wire  in  feet. 

All  insulated  cop))(>r  wire  in  feet.  (This  iiK-ludcs  outs'de  :iiid  inside  twisted 
pair,  bridle,  potliead,  and  office  wire.) 

Huzzer  wire,  in  sjhioIs.      (  Kacli  standard  spool  liolds  ono-lialt'  mile.) 

Fuse  wire,  in  pounds. 

Field  wire,  in  miles. 

Magnet  wire,  in  pt)unds. 

Messenger  strand  wire,  in  feet. 

Uesistance  wire,  in  ixnmds. 

Deep-sea  .sounding  wire,  in  fathoms. 

(368) 


Technical  Equipment  Issued  by  the  Signal  Corps. — Chapter  8.  87 

Seizing  wire,  in  ixmnds.  (This  is  a  .soft  (1.  I.  wire,  40  mils  in  diameter,  for 
serving  armor  wires  of  D.  S.  cable.) 

Annunciator  wire,  in  pounds.  (This  is  copper  wire  of  about  30  or  4(J  mils  in 
diameter,  cotton  and  paraflin  insulation.) 

Tabic  of  lengths  and  resistances  of  standard  spools  "18  per  cent  "  German-silver 

alloy  resistance  wire. 


M 

i 

Feet  per 

ounce,  appro.vimate. 

Ohms  per 

ounce,  approximate 

1    . 

6 

0-3 

^3 

a 

^ 

♦J 

J^ 

■*-> 

^ 

l^ 

8 

8 

^ 

^ 

0 
0 

8 

M 

0  g 

0)  a 

<C  0 

Wl 

c  a 

<B  a 

01 

« 

a 

•fi  2. 

■^:i 

^ 

<D 

S2 

u2 

3 

a) 

• 

p 

03 

5 

^ 

0 

a 

3 
0 

q 

^ 

§ 

a 

3 
0 

a" 

2; 

ft 

m 

ft 

M 

« 

fi 

CO 

0 

au 

n 

0 

32 

4 

19 

19 

20 

20 

20 

3.5 

3.5 

3.5 

3.6 

4.0 

18.4 

25.3 

4 

29       30 

30 

31 

32 

8.7 

9.0 

9.0 

9.1 

10.2 

30.0 

20.1 

4 

45 

48 

49 

50 

51 

21.0 

22.0 

22.0 

23.0 

20. 0 

47.0 

12.6 

2 

ino 

115 

120 

125 

130 

120.0 

135.0 

139.0 

145.0 

165.0 

119.0 

10.0 

7. 

150 

175 

185 

195 

200 

286.0 

332. 0 

345.0 

362.0 

416.0 

189.0 

8.9 

1 

ISO 

220 

/230 

245 

260 

432.0 

519.0 

537.0 

524.0 

662.0 

239. 0 

8.0 

1 

220 

270 

285 

300 

325 

658.0 

807.0 

840.0 

904.0 

1,050.0 

295.0 

7.1 

1 

270 

340 

350 

383 

410 

992.0 

1,250.0 

1,310.0 

1, 420. 0 

1,680.0 

374.0 

6.3 

1 

320 

410 

440 

480 

520 

1,490.0 

1,930.0 

2,030.0 

3, 530. 0 

4,2.30.0 

476.0 

5.6 

1 

370 

500 

540 

600 

650 

2, 200. 0 

2,970.0 

3,  ISO.  0 

3, 532. 0 

4,230.0 

602.0 

5.0 

1 

440 

610 

650 

740 

825 

3, 260.  0 

4, 580. 0 

4,880.0 

5,500.0 

6, 730. 0 

756.0 

4.5 

1 

500 

740 

800 

920 

1,040 

4,770.0 

6, 950. 0 

8,080.0 

8,410.0 

10, 700. 0 

955.0 

4.0 
3.5 
3.1 

1 
1 

1 

970 
1,150 
1,400 

1,150 
1,400 
1,730 

1,310 
1,650 
2  090 

12, 500. 0 
21, 600. 0 
29,700.0 

14,100.0 
22,000.0 
34,  700. 0 

16,900.0 
26,800.0 
42,  700. 0 

1,200.0 
1,530.0 
1,930.0 

These  values  are  approximate. 

When  ''  Climai"  resistance  wire  is  ordered,  it  should  have  a  resistance  approximately  2.777+times  that 
of  table.    The  other  vahies  for  Climax  wire  are  the  same  as  above. 

When  30  per  cent  German-silver  wire  is  ordered,  it  should  be  estimated  that  its  resistance  is  approxi- 
mately 1.55  times  that  of  18percent  wire. 

l?are  wire  will  be  supplied  in  packages  as  above.    Its  resistance,  etc.,  may  readily  be  determined  from 
data  above. 

Bare  S.  B.  wire  12.6  mils  in  diameter,  supplied  in  ounce  spools  (about  150  feet).    Resistance,  2.1  ohms 
per  foot. 

MISCELLANEOUS    FIELD   EQUIPMENT. 

WniE    CARRIER. 

The  wire  carrier  shown  in  figure  8-27  is  used  for  paying  out  or  recovering 
buzzer  wire.  It  is  also  used  for  carrying  the  antenna  and  counterpoise  of 
the  Signal  Corps  portable  radio  sets.  A  carrier  will  hold  one-half  mile  (same 
as  metal  reel)  of  buzzer  wire,  and  canvas  covers  for  them  are  supplied  when 
needed.  Wire  can  be  conveniently  paid  out  and  recovered  by  means  of  these 
reels. 


Fig.  8-27.— CARRIER,  WIRE. 
(369) 


88 


Signal  Corps  Manual  No.  3. — Chapter  8. 


HAND    REEL. 


This  apparatus  may  be  iised  for  paying  out  and  recovering  buzzer  wire. 
It  is  so  proportioned  that  the  metal  spool  \ipon  ^A'hich  buzzer  wire  is  furnished 
tits  the  trunnions,  and  by  means  of  a  crank  handle  the  spool  can  bo  revolved. 
Figure  S-28  shows  the  construction  of  this  apparatus. 


3' ^ 


Fig.  8-28.— REEL,    HAND. 
(370) 


Technical  Equipment  Issued  by  the  Signal  Corps. — Chapter  8.  89 

m/ZEli    CONNECTUK. 

Type  A. — This  form  of  connector  is  made  of  nickeled  steel,  and  should  be 
used  for  "  clippinj;  "  on  the  buzzer  wire  and  the  11-strand  field  wire.  Extra 
studs  should  be  kept  on  hand  for  repairs.  These  studs  screw  into  the  con- 
nector and  may  be  removed  If  necessary.  The  flexible  cord  should  not  be 
knotted  up  or  twisted,  as  this  tends  to  break  it.  A  type  A  connector  is  shown  in 
figure  S-29. 


Fig.  8-29.— CONNECTOR,    BUZZER,   TYPE   "A." 
PIKES,   WIRE. 

The  wire  pike  with  model  1910  hook  is  shown  in  figure  8-30.  This  hook 
is  made  of  malleable  cast  iron.  The  upper  point  is  bent  out  three-fourths  inch 
to  facilitate  picking  up  wire  by  mounted  men.  The  hook  proper  is  about  one- 
half  foot  in  length  and  is  carried  on  a  staff  of  straight-grained  hickory.  The 
complete  pike  is  9  feet  in  length. 

A  hook  with  roller  is  n(»w  being  tested,  as  continual  use  of  a  solid  hook  results 
in  the  wire  wearing  a  deep  groove  in  the  metal. 

MEGAI'IIO.VE.S,    FIHEIt.    IS-IXCH. 

The  latest  type  of  Signal  Corps  field  megaphone  is  made  of  fiber,  with 
aluminum  mouthpiece  and  leather  handle.  Tliese  megaphones  are  IS  inches 
long  and  9  inches  in  diameter  at  large  end. 

POLE.S.    LANCE,    AND   IXSCLATORS. 

These  poles  are  usually  made  of  well-seasoned,  straight-grained  pine  or 
cypress,  and  are  13  feet  11  inches  from  tip  to  tip.  The  diameter  of  the  pole 
at  the  butt  is  2  inches,  tapering  to  1*  inches  where  it  enters  the  head.  The 
butt  of  the  pole  is  shaped  to  a  blunt  point  3  inches  long.  The  top  is 
tapered  to  fit  in  a  galvanized-iron  head  3f  inches  long.  This  head  is  threaded 
externally  to  fit  the  ordinary  glass  or  porcelain  insulator.    The  end  of  the  head 

(371) 


90 


Signal  Corps  Manual  No.  3.— Chapter  8. 


Figs.  &-30.— WIRE  PIKE- 
(372) 


Technical  Equipment  Issued  by  the  Signal  Corps. — Chapter  8.  91 

is  threaded  internally  to  receive  a  corresijondingly  tlireaded  galvanized-iron 
rod  upon  which  is  molded  a  special  mica  composition  insulator.  These  special 
insulators  are  of  two  types,  the  only  difference  in  them  being  in  the  type  of 
device  for  securing  the  wire.  One  is  equipped  with  a  bent  galvanized-iron  wire 
appliance  called  fr<»m  its  shape  a  "pig-tail  insulator."  The  .second  is  a  U-shaped 
device  similarly  mounted,  called  a  "  clamp  insulator."  The  clamp  insulator  is 
employed  on  about  every  tifth  pole  of  a  lance  line,  to  prevent  a  longitudinal  move- 
ment of  the  wire,  while  the  pig-tail  insulator  is  used  upon  the  other  poles.  The 
lance  pole  weighs  about  7  pounds  and  the  galvanized-iron  head  with  insulator 
about  3  pounds. 

STANDARD    SPECIFICATIONS. 

The  following  index  to  standard  specifications  is  correct  to  August  1,  191G. 
New  specifications  are  added  and  old  ones  corrected  from  time  to  time.  Those 
marked  (*)  are  not  intended  for  general  distribution  and  are  not  in  jirinted 
form : 

A. 

♦Aeroplane  tent  (handmade) 527 

♦Ambulance,  improved,  Quartermaster  specification  for 446 

Analysis,  chemical,  of  rubber  insulating  compound 581 

Anemometer 159 

Apparatus,  zone  signal 302 

^ms,  cross,  wooden 177 

Arresters,  lightning : 229 

B. 

Bag,  service,  tool 312 

♦Balloons,   captive,   power   winch   wagon   for 541 

Balloons,  dirigible 483 

Batteries,   dry,   standard 221 

Battery,  telephone,  storage 280 

Battery,  testing,  service 185 

♦Binding  posts  and  connectors 231 

Block,  terminal,  telephone 438 

Box,   baseline,   switch 455 

Box,  cable  terminal,  weatherproof ; 245 

Box,  outlet,   for   target   ranges 471 

Box,  searchlight,  outlet 297 

Box,  submarine  cal)le  terminal,   unit   type 533 

Box,  terminal,  type  D 441 

Bracket,  handset 209 

Breast  reel 412 

Buzzers,  service  '. 5.55 

♦Buzzer  system   equipment,   target   range 496 

Buzzer  wire  and  sjwol  for  buzzer  wire 387 

Box,  transfer  switch 582 

Box,  standard  junction . 584 

C. 

Cabinet,  supply : 193 

Cable,  aerial,  paper  insulation,  type  401  to  419 197 

Cable  and  wire  to  be  used  in  wireless  telegraph  work 416 

1373) 


92  Signal  Corps  Manual  No.  3. — Chapter  8. 

Cable,  deep-sea,  singlt^  conductor 419 

Cable,  double  armor,  sinjile  conductor,   light-i ,   41!) 

Cable,  general  requirements  for 554 

Cable,  intermediate,  single  conductor 419 

Cable,  lead-covered,  rubber  insulation,  multiple  conductor 429 

Cable,  multiple  and  single  conductor,  rubber  insulation,  submarine,   F.  C. 

(single  and  double  armor) 431 

Cable,  one  pair,  rubber  insulation,   lead   sbeath,   galvanized   flexible  steel 

armor 54(5 

Cable,  paper  insulation,  submarine . 427 

*Cable,  Philippine,  single  conductor,  submai'ine 424 

Cable,  power,  rubber  insulation 432 

Cable,  single  and  multiple  conductor,  for  data  transmission  circuits 580 

Cable  splicer's  chest 318 

Cable,  submarine,  terminal  box,  iinit  type 538 

*Cable,  submarine,  three-conductor,  armored 558 

Cable,  switchboard,  twenty  pair 290 

Cable  terminals,  standard,  submarine 386 

Cable  terminal  box,  weatherproof 245 

*Cart,  wire,  model  1911,  type  H .5.52 

*Cart,  wire,  model  1911,  type  I 563 

*Cart,  wire,  model   1913,  type  K 573 

Case,  electrical  instrument 145 

Case,  reagent,  for  testing  electrolyte 315 

Cement,  Portland 391 

Charging  panel,  storage  battery , 1  .572 

Chest,  cable  splicer's 318 

Chest,  construction,  tool ^ 400 

Chest,  electrical  engineer's,  tool 192 

Chest,  mechanic's,  tool 562 

Chest,  pipe  fitter's 1 276 

Chest,  post  tool 3.50 

Compound,  30  per   cent   rubber   insulation ^ 430 

Compound,  40  per  cent  rul)ber  insulation .583 

('om])ound,  rubber  liisulatioii,  method  of  chciiiical   analysis 581 

Condenser,  panel  and  bus  bar 436 

Conduit ^ 238 

♦Connectors,  and  binding  posts 231 

Construction  material,  line  standard 272 

Construction  tools,  line ! 360 

Covers  for  motor  generators  and  boosters 442 

Cross  arms,  iron  jxiU'S,  and  fittings 226 

Cross  arms,  wooden 177 

Cylinders,  gas 494 

D. 

Distribuling  frame  anil  jiower  switclil)o;iril  lor  lire-control  swilcliboiwd  room.    .571 

i:. 

Electrical   engineer's  tool   chest 192 

Klecfrical    instrument  case 145 

Electrolyte,  reagent  case  lor  testing 1_  315 

(374) 


Technical  Equipment  Issued  by  the  Signal  Corps.     Chapter  8.  93 

Equipinont,  tiivwDrks ^ 553 

Equipment,  pack  frame,  for  i)ortal)le  wireless  telegrapli  sets 561 

Equipment,  wireless  lelegi-apli  station 566 

F. 

Field  induction  telejrrapli  set 370 

Field  telephone,  artillery  type,   model  1912 535 

*Field   wireless  set,   waf?on,  (luenclied   spark   type 540 

Fireworks  equipment 553 

Firing  signals 409 

Fittings,  iK)le  line 469 

Fixtures,  lighting,  for  switchboard  rooms 393 

Flag  kits,  li-foot,  4-foot,  and  infantry 283 

Frame,   distributing,   ami   power  switchboard   for   fire-control    switchboartl 

rr>om 571 

Frame,  pack  equiinnent.  for  portable  wirel(>ss  t(>l('gra])h  s(>ts- 561 

G. 

Galvanized-iron   wire 82 

(Jalvanizing 96 

(Jalvanometers 2~H 

Gas  cylinder 494 

(Jas-cylimler   wagon 467 

Geni'i'al  ic(|uirciueiits  for  Signal  Corps  cable  specitication 554 

General   requiremenl    s])eciticati()n . 560 

Generator,  motor,  for  charging  telephone  storage  battery 285 

Glasses,  field,  Signal  Corps  types 263 

H. 

*Hangars.  coiisi  met  ion _ 585 

IlaiKllc.   pay-oiil 413 

Ilaiid-sci   liracket : 209 

Hand-reel,   wire 323 

Heliograph,  held 246 

*Hydrogen  plant 449 


Induction  telegraph  set,  field 370 

Inspector's  pocket  kit '. 186 

Instrument  case,  electrical 145 

*Insti-umciit  wagon.   1907  iiatlei-n 452 

Insiilaliim'  coiiipouiKl.  niblHT.  ."id  i)rr  cent 430 

Insulating  compouiKJ.  rubber.  40  iier  cent 583 

liisulaling  conqxtund.  rubber,  chemical  analysis  of 581 

J. 

Junction  box,  standard 584 

K. 

Key  .«;et,  switch : 491 

Kits,  tlag,  2-foot,  4-foot,  and  infantry 283 

Kits,  inspector's,  pocket : -l 186 

Knife  switches • ^ 368 

( :'.7o  I 


94  Signal  Corps  Manual  No.  3. — Chapter  8. 

L. 

Lance  pole 376 

*Lance  truck.  1908  pattern 538 

Lanterns,  field  acetylene 265 

Lighting  fixtures  for  switchboard  rooms 393 

Line  construction  material,  standard 272 

Line  construction  tools 360 

Lineman's  magneto  testing  set 306 

M. 

Magneto  testing  set,  lineman's 306 

Masts,  180  and  130  foot,  for  wireless  telegraphy 530 

*Mast,  80-foot,  hollow  sectional,  type  E 550 

Mast,  40-foot,  hollow  sectional,  type  D 551 

Material,  splicing  and  tape 569 

Material,  standard  line  construction- __ 272 

Megaphones   136 

Motor  generator  for  charging  storage  battery '.-  285 

Molding,   wood 294 

O. 

Ohmeter    173 

Oil  set  and  accessories 407 

Outlet  box  for  target  ranges 471 

Outlet  box,  searchlight - 297 

P. 

E'ack  frame  equipment  for  portable  wireless  teU'grai)h  sets 561 

Panel  and  bus  bar  condenser 436 

Panel,  charging,  storage  battery 572 

Panel,  station  switch l 415 

Panel,  time-interval,   switch 568 

Pay-out  handle 413 

Pay-out  reel . 91 

Pipe  fitter's  chest - 276 

♦Plant,  hydrogen 449 

Pocket  kit,  inspector's 186 

Pole  line  fittings --  469 

Poles,  iron,  iron  cross  arms  and  fittings 226 

Poles,   lance 376 

Pole  seat 377 

Portland  cement 391 

♦Posts,  binding  and  (:'onnectors 231 

Post   tool   chest 350 

Preservatives,  wood 570 

I'rlmary  battery  supplies 341 

R. 

Ftcagent  (iisc  fur  testing  electrolyte 315 

Keel,   breast 412 

I{eel,  hand,  wire 323 


(376) 


Technical  Equipment  Issued  by  the  Signal  Corps. — Chapter  8.  95 

Reel,  pay-out 91 

Keel,   take-up 95 

Requirements,  preneral   specification 560 

Kuljher-insulatiiif^  conipouiul.  3t>  per  cent 430 

Hul)l»er-insulatiny  compound,  40  per  cent 583 

Rubber-insulating  compound,  method  of  chemical  analysis  of 581 

S. 

Seat,   pole 377 

Service  testing  battery 185 

Service  tool  bag 312 

*Set,  field  wireless  wagon,  quenched  spark  type 540 

Set,   induction,  field  telegraph 370 

Set,  portable  wireless,  pack  frame  equipment  for 561 

Sets,  lineman's  magneto  testing ^ 306 

Signal  apparatus,  zone 302 

Signals,    firing 409 

Splicer's   chest,    cable 318 

Spool  for' buzzer  wire,  and  buzzer  wire 1 387 

Station  switch  panel ^ 415 

Storage   battery,    telephone 280 

Storage  battery,  charging  panel 572 

Supplies,    primary    battery 341 

Supply  cabinet 193 

Switches,   knife 368 

Switchboard,  camp  telephone 578 

Switchboard,  power,  and  distributing  frame,   for   fire  control  switchboard 

room J 571 

Switchboard  rooms,  lighting  fixtures  for/ 393 

Switchboard,  telephone,  common  battery  type 321 

Switchboard,    telephone,    power 519 

Switch  box,  base  line 455 

Switch   key   set 491 

Switch  boxes,  transfer 582 

T. 

Take-up  reel 95 

Tape,  and  splicing  material 569 

*Target  range  buzzer  system  equipment 496 

Target  ranges,  outlet  box  for 471 

Telegraph    set,    induction,    field 370 

Telephone,   artillery    type,   composite 401 

Telephone,  camp 577 

Telephone,  common  battery 320 

Telephone,  common  battery,  artillery  type 575 

Telephone,   Field  Artillery 535 

Telephone,    local   battery 361 

Telephone,   storage  battery •_ 280 

Telephone  switchboard,  common  battery 321 

*Tent,  aeroplane,  handmade 527 

*Tent  for  housing  dirigible  balloon 497 

Terminal  block,  telei)hone 438 


(377) 


96        *  Signal  Corps  Manual  No.  3. — Chapter  8. 

Terminal  box,  type  D 441 

Terminal  boxes,  cable,  submarine,  unit  type 533 

Terminal  boxes,  cable,  weatherproof-^ 245 

Terminals,  cable,  standard,  submarine 386 

Testing  battery,  service 185 

Testing   set,    lineman's,    magneto 306 

Test,  tinning,  for  copper  wire 403 

Test,  tinning,  for  iron  or  steel  wire 414 

Thermometers,  mercurial 144 

Time  interval  switch  panel 568 

Tinning  test  for  copper  wire 403 

Tinning  test  for  iron  or  steel  wire 414 

Tool  bag,   service 312 

Tool    chest,    construction 400 

Tool  chest,  electrical  engineer's _ 192 

Tool   chest,   mechanic's 562 

Tool   chest,   post 350 

Tools,   line  construction 360 

Tower,  steel,  for  wireless  telegraph  station 510 

♦Transformer,  testing . — 476 

*Truck,  lance 538 

Transfer  switch  box 582 

V. 

Vane,  wind 256 

Vulcanizer,    electric : 524 

W. 

♦Wagon,  gas  cylinder 467 

*Wagon,  instrument 452 

*Wagon,   power   winch,   for   captive  balloons 541 

*Wagon,  2-horse  and  4-horse  or  mule   (Quartermaster  specification) 445 

*Watch,  stop 308 

Watch,   wrist 579 

Wind   vane 256 

Wires  and  cables  to  be  used  in  wireless  telegraph  work 416 

Wire,  buzzer,  and  spool  for  buzzer  wire 387 

Wire,  copper,   line 79 

Wire,  field,  11-strand 408 

Wire,  field,  twin  conductor,  mountain  artillery  type 548 

Wire,  galvanized  iron 82 

*Wire,  hard  drawn,  weatherproof,  copper _ 307 

Wire,  inside  twisted  pair,  pot-head  and  bridle 340 

Wire,  No.  17  gauge,  copper  clad  steel,  twisted  pair,  outside  distributing-.  557 

Wire,  oflice,  single,  inside 418 

Wire,  outside  twisted  pair,  copper  conductors 396 

Wire,  pot-head,  inside  twisted  pair  and  bridle 340 

Wire,  single,  inside,  office 418 

Wire,  single,  rubber  covered  and  braided 474 

♦Wire,   standard    electrical    condu<'tors 576 

♦Wire,  weatherproof,  hard-drawn  copper 307 

(378) 


Technical  Equipment  Issued  by  tlic  Signal  Corps.     Chapter  8.  97 

Wire,  zone  signal ^ 351 

"■Wireless  set,  Held  wnfxoii,  quenched  sjiark  type 540 

*Wireless  sets,  portal)le  i)ack  Iraiiic  eciuipment  for 561 

Wireless  lolc.ixrapli  station  e»iuii»iiient 566 

Wireless  telegraph  station,  steel  tower  for 510 

Wireless  work,  wire  and  cable  to  be  used 416 

Wooden  (;ross  arms 177 

Wood  molding 294 

Wood   preservatives 570 

Z. 

/one   signal    apparatus 302 

Zone  signal    wire 351 

An  enumeration  of  all    Signal    Corps  blank  forms   may   be  found  in   Signal 
Corps  Manual  No.  7,  latest  edition. 


40581"— 17 25  (379) 


Chapter  9. 
MISCELLANEOUS   TESTS   AND   GENERAL   INFORMATION. 

MISCELLANEOUS   TESTS. 

The  importance  of  testinjr,  hoth  for  regularly  ascertaining  the  condition  of  the 
lines  with  a  view  to  anticipating  breakdowns  and  as  a  means  of  locating  faults 
when  they  occur,  is  something  that  should  he  recognized  by  all  ofticers  and 
enlisted  men  on  duty  in  connection  with  maintenance  of  Signal  Corps  installa- 
tions. 

The  following  notes  on  cable  testing  and  the  location  of  faults  where  accurate 
instrumeids  are  not  availal)le  will  be  found  of  great  value  where  apparatus  must 
be  improvised. 

The  extensive  use  of  short  subterranean  and  submarine  cables  for  tire-control, 
post-telephone,  and  submarine-mine  systems  generally,  makes  some  method 
of  easy  testing  desirable.  A'ery  often  testing  sets  are  not  on  hand.  If  on 
hand,  they  may  be  out  of  order  or  there  may  be  nobody  available  who  is  sufTi- 
ciently  skilled  in  their  use  for  location  of  faults.  By  far  the  most  common  class 
of  faults  is  that  due  to  defects  in  insulation.  It  is  desirable  to  locate  these  in 
submarine  cables,  and  very  necessary  in  case  of  multiple-core  cables  buried  in 
trenches  or  drawn  into  conduits,  which,  of  course,  prevents  their  being  readily 
taken  up  for  examination. 

In  the  absence  of  better  instruments,  a  fairly  good  idea  of  the  insulation  re- 
sistance of  a  cable  may  be  arrived  at  by  means  of  a  battery  and  telephone 
receiver,  as  follows : 

A  telephone  receiver  (T)  (tig.  9-1)  is  connected  with  the  battery  (B)  of  a 
few  cells,  the  latter  being  connected  with  the  cable  armor  at  C.  A  well-insu- 
lated wire  (/)  is  connected  with  the  other  terminal  of  the  telephone.  The  ends 
of  the  conductor  are  prepared  and  insulated  as  above  described.  When  the  end 
of  /  is  touched  on  the  cable  conductor  a  click  is  heard  in  the  receiver.  If  after 
about  one  second  it  is  touched  again  and  no  click  is  heard  in  the  receiver,  the 
insulation  resistance,  if  one  cell  of  battery  is  used,  is  above  about  50  megohms ; 
if  two  cells  of  battery,  100  megohms,  ami  so  on,  for  about  the  proportion  of  cells. 

The  click  produce*!  on  first  contact  is  due  to  the  current  rushing  in  to  charge 
the  cable ;  and  if  the  insulation  is  good,  in  one  second  so  small  an  amount  of 
this  charge  will  be  lost  by  leakage  that  little  or  no  sound  will  be  produced 
by  subsequent  contacts,  as  cable  will  still  be  charged.  Care  should  be  taken 
that  wire  /  and  telephone  terminal  attached  to  it  are  well  insulated,  other- 
wise leakage  from  them  may  give  false  indications. 

Having  found  the  faulty  conductors,  the  location  of  these  faults  may  then 
he  proceeded  with  by  the  method  suggested  below  (figs.  9-2  and  9-3).  It  is 
applicable  to  cables  having  two  or  more  similar  conductors,  or  to  a  single- 
conductor  cable  when  both  ends  are  available,  as  when  it  is  coiled  in  a  tank  or 
on  a  reel.  It  is  the  ^Murray  loop  test  with  a  "  slide  wire "  in  which  simple 
relations  of  resistance  to  lengths  exist,  owing  to  the  uniformity  of  resistance 
along  the  wires  in  the  cable  conductors  and  slide  wires,  respectively.  It  is, 
in  fact,  a  combination  of  several  well-known  instrument  methods, 

(381)  1 


Signal  Corps  Manual  No.  3. — Chapter  9. 


Fig.  9-1.— TEST,    EMERGENCY,    INSULATION. 

To  prevent  serious  errors  care  must  be  taken  that  oih>  of  tlie  conductors  in 
this  test  has  sound  insulation. 

No  resistance  measurements  are  involved,  and  the  only  apparatus  required 
is  a  few  cells  of  battery,  a  telephone  receiver,  and  from  10  to  50  feet  of  bare 
resistance  wire.  Of  this  latter  about  No.  28  "  Climax  "  or  "  S.  B."  wire  is 
suitable.  However,  if  resistance  wire  is  not  to  be  had,  fair  results  may  be 
obtained  by  using  No.  36  bare  copinn-  wire. 


■Y- 


Flg.    9-2.— TEST,     LOCATION    OF    FAULTS    WITH     IMPROVISED    APPARATUS,    USING    A 

TELEPHONE    RECEIVER. 


I''ii-st  taking  liic  case  of  a  nniltiple-conductor  cable,  say  .'?,()()<)  yards  l(»ng.  in 
whicli  tiicrc  arc  one  or  more  (-(inductors  witli  delVctive  insulalidii  and  at  least 
one  good  one.  .loin  tlic  (Idcil  ivc  imc  tn  be  Icslcd  Willi  liic  gdiKl  inic  .-it  th(> 
djslani  ciKJ.  Di-ivc  two  sni;ill  liriglil  nails  (.1  and  ('  in  lig.  1»  "J)  (•(.nvcMiciil  to 
(lie   terminals  ol'   the  ( (•ndudors   ;il    the   testing  end    and    stretch    froni    tlie.se  a 

(382) 


Miscellaneous  Tests  and  General  Information. — Chapter  9.  3 

piece  of  the  resistance  wire  aiduiid  another  nail  (D)  and  bade,  malving  each 
equal  branch  of  tlie  wire  A  I)  and  C  D  of  sucli  a  lengtli  as  to  be  some  exact 
subnuiltiple  of  tlie  length  of  the  cable  being  tested.  For  example,  have  each 
branch  of  the  wire  in  this  case  three  thousand  thirty-seconds  of  an  inch  long, 
or  ^^  (93.7"))  inches.  Join  one  of  the  two  nails  at  the  end  of  the  cable  termi- 
nals to  the  defective  cable  conductor,  the  other  nail  to  the  good  conductor. 
Join  one  terminal  of  the  telephone  receiver  li  to  the  ground  and  the  other 
terminal  to  a  short  wire,  which  will  be  used  as  a  "  searcher."  Connect  a  few 
cells  of  battery  B  across  the  nails  to  which  the  cable  terminals  are  attached. 
Now,  putting  the  telephone  receiver  to  the  ear,  feel  along  the  resistance  wire, 
which  is  attached  to  the  defective  conductor,  with  the  searcher  wire  attached 
to  the  telephone.  A  point  G  will  be  found  where  the  frying  sound  produced  in 
the  telephone  will  cease,  and  if  the  searcher  wire  be  moved  either  way  from 
this  it  will  again  become  audible.  Mark  this  point  on  the  resistance  wire,  re- 
verse the  connections  of  the  battery,  and  again  find  the  point  of  silence.  If  it 
is  not  coincident  with  the  first,  take  the  mean  position  between  them. 

The  distance  of  this  point  G,  in  thirty-seconds  of  an  inch,  from  the  nail  C 
to  which  the  defective  cable  terminal  is  attached,  is  the  distance  in  yards  from 
the  cable  terminal  to  the  fault. 

It  is  evident  that  for  short  cables  greater  accuracy  is  .secured  by  taking 
larger  representative  units  in  proportion  for  the  resistance  wires.  For  ex- 
ample, if  the  cable  were  1.250  yards  long,  the  units  on  the  resistance  wires 
could  be  sixteenths,  and  the  wires  be  convenient  in  length:   ^[f|^=TSJ  inche.s. 

Care  should  be  taken  to  stretch  the  resistance  wires  evenly  and  not  wrap  the 
loose  ends  back  on  the  stretched  portion,  as  that  would  destroy  the  uniformity 
of  resistances  throughout  the  length  on  which  the  assumed  proportion  depends. 

In  testing  a  defective  single-conductor  cable  the  two  ends  are  joined  to  the 
resistance  wire,  as  just  stated,  the  tchole  length  of  the  resistance  wire  being 
in  some  simple  proportion  to  the  length  of  the  cable. 

For  example,  if  the  cable  is  1,980  yards  long,  the  whole  length  of  the  re- 
sistance wire  would  be  ^f-f^  or  ^^  inches,  as  desii'ed — the  greater  length 
giving  tlie  result  with  greater  accuracy.  It  will  be  readily  seen  that  this  and 
the  former  case  are  identical,  as  the  "  loop "  formed  by  joining  the  distant 
ends  of  two  multiple  conductors  is  in  this  case  replaced  by  the  "  loop  "  of  the 
single  conductor. 

The  method  of  securing  ends  of  wires  by  nails  is  given  to  show  with  what 
ease  and  simplicity  the  necessary  parts  for  the  test  may  be  set  up.  But  even 
roughly  and  hastily  set  up,  the  test  will  locate  faults  with  surprising  accu- 
racy if  a  sufficient  length  of  resistance  wire  be  used  to  eliminate  small  acci- 
dental irregularities  in  attachments  of  wires. 

The  test  is  a  simple  application  of  the  Wheatstone  bridge  principle.  It 
may  be  of  interest  to  trace  this  out  (fig.  9-2). 

A  K  and  C  K  are  the  two  cable  conductors  joined  at  the  distant  end  K. 
The  lower  one  is  defective  at  some  unknown  point  H.  The  resistance  wire 
A  D  C  is  joined  np  as  shown  with  the  cable  conductors  and  battery  B.  The 
point  of  silence  in  the  telephone  is  found  at  G.  The  Wheatstone  bridge  rela- 
tion of  resistances  then  exists  in  the  lengths  of  the  wire,  X  :Y : -.E  -.F.  And 
since  these  resistances  are  along  uniform  wires  the  same  relations  exist  be- 
tween IcniitJis  as  between  resistanrcs.  Consequently  E  can  be  read  off  di- 
rectly in  the  terms  of  A'  if  the  lengths  .1  D  and  C  D  are  laid  off  numerically 
equal  to  A  K  and  C  K. 

The  foregoing  method  involves  no  computation.  It  is  evident  from  the 
above   proportion   that   if  the  entire   length   of   resistance   wire   were   made 

(383) 


Signal  Corps  Manual  No.  3. — Chapter  9. 


some  even  number  of  any  convenient  nnit  (say  sixteenths  of  an  inch)  that 
a  substitution  of  values  in  the  proportion  would  give  the  distances.  For 
example,  if  the  resistance  wire  had  a  length  of  1,000  and  balance  were  found 
at  432  from  the  end  to  which  the  faulty  conductor  was  attached,  the  distance 
to  the  fault  would  be  432/1,000  of  the  entire  length  of  the  conductors,  or 
432/1,000X2  of  the  length  of  the  eable  from  the  testing  point. 

By  this  method,  involving  simple  computations,  the  same  wire  stretched  on 
a  convenient  board  may  be  iised  for  all  measurements.  It  becomes  in  effect 
an  ohmmeter. 

If  more  than  one  faulty  place  exists  in  the  conductor,  the  test  will  give 
approximately  the  mean  position.  So,  having  made  the  test  and  cut  the  cable 
at  the  indicated  place,  test  both  ways  to  ascertain  if  both  parts  are  not  de- 
fective. If  sound  toward  either  station,  the  fault  should  be  relocated  in  the 
defective  part. 

It  will  probably  be  found  near  the  position  of  the  tirst  cut  and,  having  allowed 
a  reasonable  percentage  error,  on  the  second  cut  it  is  highly  probable  the  faulty 
section  will  be  cut  otf.  It  has  been  found  that  generally  the  error  of  determi- 
nation will  fall  within  1  per  cent. 


■O 


Fig.    9-3.— TEST,     LOCATION    OF    FAULTS    WITH     IMPROVISED    APPARATUS,    USING    A 

GALVANOMETER. 

A  word  may  be  said  regarding  the  telephone  receiver  as  a  detector  of  feeble 
currents.  It  is  much  more  .sensitive  than  the  average  pivoted  galvanometer  and 
will  stand  infinitely  more  abuse.  However,  in  noisy  places  Uie  galvanometer 
may  be  substituted  for  the  telephone  in  this  test. 

If  the  fault  has  a  high  resistance,  so  that  the  four  or  five  cells  of  battery 
perimssible  in  tlie  manner  of  connecting  .shown  in  diagram  can  not  send  .sufR- 
<-ient  current  through,  then  some  form  of  rather  sensitive  galvanometer  becomes 
necessary  with  the  increased  battery  and  change  of  connections  recpiired.  In 
place  of  the  battery  in  figure  9-2,  connect  the  galvanometer.  In  i)lace  of  the 
telephone  receiver,  connect  a  battery  of  from  20  to  100  cells  in  series.  Then 
proceed  as  with  the  telei)hone  receiver,  noting  that  for  each  break  or  irregularity 
of  contact  of  the  searcher  wire  there  may  be  n  kick  of  the  galvanometer,  due 
to  capacity  or  inductance,  and  that  l)alance  is  obtained  only  when  the  galvanom- 
eter .shows  no  deflection  when  the  searcher  wire  is  at  rest.     (Fig.  9-3.) 

A  fault  in  a  single  conductor  cable,  or  one  involving  all  the  conductors  of  a 
multiple  cable,  may  be  located  if  two  additional  wires  of  sound  insulation 
between  the  p«>ints  connected  by  the  faulty  cable  are  available. 

As  the  lengths  and  resistances  of  these  wires  are  immaterial,  temporary  or 
roundabout  wires  may  be  utilized. 

(384) 


Miscellaneous  Tests  and  General  Information. — Chapter  9.  5 

Tlic  nicdiod  of  jirocodurc  is  ;is  follows:  Strotfli  a  sinj:;U'  piece  of  resistance 
wire  y\  li  ( fi^riires  9-4  aiul  \)-~>)  wliose  leiifrth  is  some  even  number  of  parts,  say. 
1,000  sixteenths  of  an  incli.  Tlie  two  sound  outside  wires  /  and  A'  and  flie  d«'- 
fective  one  />  are  c(»nnected  at  tlie  distant  end.  The  fjalvanometer,  i)attery.  and 
searcher  are  connected,  as  sliown  in  fij^ure  9—1,  and  tlie  point  of  balance  ob- 
tained.    Call  the  reading  A  from  the  point  C. 


Fig.    9-4.— TEST,    LOCATION    OF    FAULTS    WITH    IMPROVISED    APPARATUS,    ALL   CON- 
DUCTORS   FAULTY. 


Then  connect  up  as  in  figure  9-5,  joining  the  battery  to  earth -or  to  tlie  cable 
sheath.  If  the  fault  appears  as  a  leak  between  two  adjacent  wires  of  the 
multiple  cable,  the  lower  end  of  the  battery  should  be  joined  to  the  other  faulty 
wire  instead  of  the  cable  sheath  or  ground. 


Fig.   9-5.— TEST,    LOCATION    OF    FAULTS    WITH    IMPROVISED    APPARATUS,    ALL   CON- 
DUCTORS  FAULTY. 

(385) 


6  Signal  Corps  Manual  No.  3. — Chapter  9. 

WIkmi  hMliUici'  is  (il>t:iiiU'(l.  note  llic  leading  on  tlic  rcsisliincc  wire  from  i)()iiit 

('.    Call  it  A'.    Then  if  lenjrtli  of  rauity  roiiductor  is  J.  ftvt,  tlic  distant'  of  the 

A'  L 
fault  from  C  is  — r— feet. 
A 

This  method  is  particularly  applicable  to  paper  cables  where  a  leak  has  iimile 

the  insulation  of  all  the  conductors  faulty. 

Location  of  break  in  conductor. — The  method  applicable  when  the  wire  is 
broken  inside  the  insulation,  leaving  the  latter  intact,  is  given  below.  This  is 
the  character  of  the  fault  generally  produced  when  a  conductor  parts  in  a 
paper-insulation  cable.  Owing  to  the  small  capat-ity  of  this  kind  of  cable 
the  method  is  useful  because  of  the  practical  difficulty  in  getting  correct 
capacity  values  by  galvanometer  methods  in  small  lengths  of  this  cable. 

The  connections  for  the  test  are  the  same  as  that  described  in  figure  9-3, 
except  the  telephone  receiver  is  used  in  place  of  the  galvanometer.  The  point 
H,  instead  of  representing  a  fault  in  insulation,  in  this  case  represents  the 
location  of  a  break  in  the  wire.  It  is  best  to  use  quite  a  number  of  cells,  say  20 
or  30,  if  available.  The  battery  circuit  is  reversed  and  interrupted  rapidly  while 
a  point  is  sought  with  the  searcher  along  the  resistance  wire  where  the  clicks 
are  no  longer  heard  in  the  receiver.  When  this  point  of  balance  is  reached  the 
distance  to  the  break  is  then  read  off  on  the  scale  along  the  resistance  wire 
from  C  to  the  point  6',  as  explained  in  locating  insulation  faults.'  In  this  case 
the  point  G  is  in  the  corresponding  position  on  the  upper  wire.  The  reason  for 
this  is  that  this  wire  having  the  greater  capacity  is  charged  lln-ough  the  bridge 
arm  having  the  lower  resistance. 


Fig.  9-6.— TEST,   LOCATION   OF  FAULTS  WITH    IMPROVISED  APPARATUS,  CON  DUCTOR 

PARTED. 

In  the  last-named  test  an  interru])led  current  of  rather  high  voltage  is  re- 
quired. A  method  of  getting  this  with  only  two  (h-y  cells  is  to  take  a  local  bat- 
tery telephone  induction  coil  (/  in  the  ligure)  and  allach  it  to  a  wooden  base, 
together  with  an  ordinary  small  nu^tal  buzzer  "  />'." 

The  connections  ai-e  as  shown  in  tigure  D-C).  When  I  lie  battery  is  connected 
tlie  buzzer  sends  a  vibratory  current  through  the  piiniary  coll.  .\  vibrat(»ry 
iiiiTcnt  of  nnich  higher  voltage  is  induced  in  the  secondary,  and  this  is  utilized 
in  place  of  the  ballery  cun-eiils.  as  shown  in  the  ror-egoiiig  tests. 

IIIK   \(>I.I'.MK'1KK    AM)    A  M  M  K  I'Ki:. 


On  land  telegrai»li  lines  and  the  aiii>aratus  connected  therewith  the  electrical 

uruls  with  wbicli  we  are  usually  concei-ned  in  nieasureinenls  an<l  tests  are  those 

given  in  Ohm's  law — the  current  in  amperes  (Miuals  the  electromotive  force  in 

volts  divided  by  the  resistance  of  the  circuit  in  ohms;  expre.ssed  algebraically, 

E 
^—jy       The  galvanometer,   in  one  or  the  other  of  its   foiMus,  measures  current. 

When  of  low  resi.stance  and  graduated  properly,  it  is  called  an  amju'remeter  or 
annneler.  When  of  high  resistance,  since  the  current  llowing  through  it  is  prac- 
tically  indejiendent   of  I  he  relatively  small   variations  of  outsiile  I'esislunce,  Ww 


Miscellaneous  Tests  and  General  Information. — Chapter  9. 


Kalviiiiuiiu'ter  n'Mdinjis  arc  dii'cctly  iiroiHirtioiiiil  lo  llic  ck-rtruiiiDl  ivc!  force  E. 
And  when  properly  f^raduated  it  becomes  a  voltmeter.  The  ammeter  and  volt- 
meter, on  account  of  portability  and  quickness  and  accuracy  with  which  read- 


Pig.  9_7._TEST,  measuring   OHMIC    RESISTANCE    BY   MEANS    OF    VOLTMETER  AND 

MILLIAMMETER. 

ings  are  taken,  are  very  satisfactory  Instruments  for  telegraph  testing.  It  is 
evident  if  /  and  E  are  measured  by  an  ammeter  and  voltmeter,  respectively, 

that  It  becomes  known — for  according  to  Ohm's  law  R=  j.     For  example,  if  we 

connect  the  ammeter  A,  battery  B,  and  a  resistance  coil  C  together,  as  in  figure 
9-7,  we  may  read  the  current  flowing.  The  small  current  commonly  used  in 
telegraphy  is  conveniently  expressed  in  milliamperes,  and  the  ammeter  grad- 
uated for  these  is  called  the  milli-  or  mil-ammeter.  If  we  attach  a  voltmeter  V 
to  the  terminals  <»f  the  resistance  coil  C\  it  will  give  the  difference  of  potential 
(E.  M.  F. )  produced  at  these  two  points  l)y  the  current  flowing  between  them. 

.Suppose  the  milliammeter  reads  28  milliamperes  (0.()2S  ampere)  and  the  volt- 
meter 4.23  volt.>^ 


JP  4  OQ 

Substituting  in  /?  ==     ,   /?  =  --^=151  ohms.    The  general  rule 
1  .  U2o 


in  connecting  up  the  annneler  and  voltmeter  for  such  measurements  is  to  put  the 
annn«>ter  in  the  circuit,  and  the  voltmeter  shunting  the  part  of  the  circuit  whose 
resistance  is  desired.  The  lU'actical  use  of  the  instruments  in  testing  telegraph 
lines  is  given  below. 

The  theoreticid  connections  are  shown  in  figure  9-S,  the  voltmeter  being  c«»n- 
nected  in  shunt  to  line  and  ground,  and  the  milliaunneter  in  series  in  tlie  circuit. 


HA/£ 


-y^if&^fs» 


'^fffl^- " 


Fig.  9-8.— TEST,    MEASURING   OHMIC    RESISTANCE   OF  TELEGRAPH    LINE   BY    MEANS 
OF    VOLTMETER  AND    MILLIAMMETER. 

(387) 


8 


Signal  Corps  Manual  No.  3. — Chapter  9. 


The  correspondence  of  this  with  figure  9-7  will  he  noted.  Tlie  practical  con- 
nections are  shown  in  figure  9-9. 

A  portable  voltmeter  I'eading  to  200  volts  (D.  aiid  luillianinieler  reading  to 
150  millianiperes  (-1),  are  mounted  on  a  Ijoard  and  connected  with  tlie  regular 
switchboard  cord  and  wedge,  as  shown,  the  other  terminal  of  the  voltmeter 
being  connected  with  the  ground. 

When  the  wedge  is  inserted  in  any  line  spring  jack,  the  ammeter  is  con- 
nected in  the  circuit  and  the  voltmeter  slumted  to  the  groiind,  as  shown  in 
figure  9-9.    The  deflections  of  tlie  ammeter  and  the  voltmeter  thus  give  /  and  E 

in  the  formula  R  =y  and  the  resistance  becomes  Icnown. 


TO    GJfOC/^O 


Pig.  9_9. —TEST,    MEASURING   OHMIC    RESISTANCE   OF    TELEGRAPH     LINE    BY    MEANS 
OF    VOLTMETER    AND    M  I  LLIAM  M  ETER,    PRACTICAL    CONNECTIONS. 

To  test,  cut  off  battery  at  most  distant  station,  ground  line,  and  take  read- 
ings. Now  open  the  key  for  a  few  seconds  and  take  a  second  set  of  readings. 
Repeat  this  process  with  all  stations  up  to  the  nearest  one.  The  readings 
with  stations  grtmnded  give  resistance  of  line  (including  relay)  to  each,  while 
readings  with  tlie  keys  opened  would  give  the  insulation  resistance  to  each. 

The  following  shows  some  methods  of  using  the  voltmeter  alone  for  various 
measurements  when  the  ammeter  is  not  available: 

THH  VOl.T.METER    (O-'i,  0-150  VOI.TS   P.^TTKRN). 

This  instrument  is  a  galvanometer  of  the  D'Arsonval  class,  in  which  a  pivoted 
coil,  controlled  by  a  spiral  spring  turning  in  jeweled  bearings,  carries  a  light 
nluminnm  pointer  moving  over  an  equally  divided  scale. 


Fig.  9-10.— TEST,  WITH  VOLTMETER,  VOLTAGE  OF  A  BATTERY. 

This  coil  turns,  when  a  current  passes  llirougli  it,  in  llie  strong  field  between 
the  poles  of  a  powerful  permanent  magnet.  In  the  base  are  two  resistance 
coils,  one  or  the  other  of  which  is  always  in  .series  with  the  movable  coil, 
dejtending  ui)on  which  scale  is  used — the  IHO  or  5  volt  .scale. 

Ciiiition. — To  i>revent  l)ending  the  i)ointer  by  violeid  action,  always  test  first 
with  the  l.^iO-volt  scale.  If  the  jioinfer  indicates  less  llian  .^>  volts,  use  the  other 
binding  iiost  and  take  advantage  of  the  greater  accuracy  of  the  5-volt  scale. 


(388) 


Miscellaneous  Tests  and  General  Information. — Chapter  9.  9 

TO  TEST  TUE   VOLTAGE  OF  A   BAT'lERY   oF  A    NUMBER  OF  CELLS. 

Use  the  150-v()lt  scale  and  connect  up  as  shown  (fig.  9-10). 
For  not  more  than  .'}  sal  aiiiiiioiiiac,  4  l)hH'slone.  or  2  storajic  colls  in  .series 
use  the  5-voIt  scale. 


Fig.   9-n.— TEST,    WITH    VOLTMETER,    DIFFERENCE    OF    POTENTIAL    BETWEEN    TWO 

POINTS  ON  WIRE. 

TO    MEASrRE    THE    DIFFERENCE    OF    POTENTIAL     (PRESSURE)     BETWEEN    ANY    TWO    POINTS    OF    A 
WIRE  OR  EXTREMITIES  OF  A   COIL   CARRYING  A   CURRENT. 

The  connections  indicated  in  figures  9-11  and  9-12  would  give  the  differences 
of  potential  at  the  two  points  on  the  wire,  or  at  the  extremities  of  the  coil, 
respectively. 


Fig.  9-12.— TEST,   WITH    VOLTMETER,    DIFFERENCE  OF    POTENTIAL  AT    EXTREMITIES 

OF  A   COIL. 

TO    MEASURE   A    RESISTANCE. 

To  measure  a  resistance  less  than  3.000  ohms  use  two  or  three  dry  or  Gonda 
cells  in  series,  get  their  voltage,  using  the  o-volt  scale.  Call  this  V.  Then  con- 
nect up  with  the  unknown  resi.stance  X  (fig.  9-13),  as  shown,  and  call  this 
scale  reading  V. 

The  resistance  of  the  volmetcr,  using  .Vvolr  .scale,  is  given  in  the  sliding  cover 
of  box.     Call  this  R. 

Then 

R(V-n 
V 

This  is  very  inaccurate  for  resistances  of  only  a  few  ohms  unless  the  resist- 
ance of  the  battery  is  taken  into  account. 


(389) 


10 


signal  Corps  Meinual  No.  3. — Chapter  9. 


In  measuring  resistances  from  3,000  to  1250,(KH)  olnns  use  tlie  150  scale,  noting 
tlie  value  of  R  given  on  tlie  cover  for  tliis.  The  same  connections  and  formula 
are  applicable. 


imii-. 


Fig.  9-13.— TEST,   WITH    VOLTMETER,  TO    MEASURE   OHMIC    RESISTANCE. 

To  secure  greater  acciiracy  in  either  of  above  cases,  tlie  battery  should  have 
sufficient  E  M  F  to  bring  the  value  of  V  as  near  5  or  150  as  practicable. 

Example. —  (1)  Using  5- volt  scale.  Resistance  to  be  measured  (A')  is  an 
ordinary  telegraph  relay  magnet. 

Suppo.se  i?=520.  Three  cells  dry  battei-y  in  series  give  T=4.35  volts.  When 
X  is  connected  in.  T^'=3.40. 

Then 

^    520(4.35-3.40)     ^^^  „„  , 
X= ^^^0 =145. 29  ohms. 

(2)  Using  150-volt  scale.  Determine  the  insulation  resistance  of  110-volt 
storage  battery  (leakage  from  either  pole  of  battery,  or  its  connections,  to 
earth ) . 

Suppose  7»'  for  this  scale=15,o00  ohms.  Voltage  across  terminals,  V=110 
volts;  voltage  between  (tne  of  the  terminals  and  eartli    (T')=12  volts. 

„     15.500(110-12)     ,„„,„„    , 
A= ^j2 ^=126,583  ohms. 

This  would  indicate  a  slight  leak,  probably  at  or  neai-  llu'  negative  end  of 
battery  if  the  tests  were  made  at  the  positive  terminal. 

If  some  coils  of  known  re.sistance  ai-e  available,  rcsistamcs  (-m  lie  measured 
more  accurately  as  follows : 

The   known    coil    and    the   resistance   to   be    measured,    marked    respectively 
r  and  x,  are  connected  with  each  other  and  a  battery,  as  shown    (tig.  9-14). 
The  voltmeter  is  connected   first  as  indicated  by  the  full   and   then  as  by   the 
broken  lines.     If  the  voltage  indicated  in  the  first  ca.se  is  /■-'  and  in  the  second 
it  is  /■;', 

E'r 


E.T<y  ■.-.r-.x.     :.x  =  - 


E 


I'se  enough  battery  to  make  a  good  rcadnlile  dellection,  and  if  several  known 
coils  are  available  use  the  one  which  is  somewhere  near  the  resistance  to  be 
measured. 

Example. — Known  coil,  10  ohms.  \'olt meter  shunt iiig  this  gave  3.2  volts,  and 
shunting  the  unknown  gave  4.7  volts.      Hence 

x='^'^><}^.=14,7  ohm.s. 
3.2 

(390) 


Miscellaneous  Tests  and  General  Information. — Chapter  9. 


11 


Fig.   9-14.— TEST,    WITH     VOLTMETER,   TO     MEASURE    OHMIC    RESISTANCE,    USING    A 

KNOWN    RESISTANCE. 

TO    MEASURE   CIRKE.NT   WITH    THK   VuLTMETEK. 

If  we  know  the  resistance  of  a  wire  or  foil,  and  liave  a  steady  current  flowing 
through  it,  tlie  voltmeter  wires  applied  at  tlu'  terminals  of  the  wire  or  coil  will 

give  a  certain  deliection,  E.    Hence,  since  ■-^=r,.  if  \v«  substitute  for  /v  and  It 

the  known  values  we  get  /.     (Connections  shown  in  figs.  9-11  and  0-12.) 

Example. — A  certain  current  is  flowing  through  a  4-ohm  telegraph  .sounder. 

When  the  wires  from  the  voltmeter    (5-volt  scale)    arei  connected  at  sounder 

binding  jiosts,  the  voltmeter  indicates  0.8  volt. 
Substituting  as  above, 

c 

/=— =.2  ampere. 

TO  RIEASIIIE  THE   INTEUXAL   I.ESISTAXCE  OF  A  BATTERY. 

Using  the  H-volt  scale,  first  take  the  voltage  of  the  cell.  Then  take  the 
voltage  at  the  terminals  of  a  coil  of  rather  low  resistance  (a  4-ohm  sounder, 
for  instance),  in  circuit  with  the  cell  (fig.  I)-12).  being  careful  not  to  close 
battery  circuit  until  ready  to  read  the  voltmeter.  Multiply  the  voltage  of  the 
cell  by  the  resistance  of  the  coil  and  divide  by  the  voltage  at  terminals  of 
coil.  From  the  result  subtract  the  resistance  of  the  coil.  The  remainder  is 
ihe  internal  resistance  sought. 

Example. — The  voltage  of  a  dry  cell  is'  1.41,  and  the  voltage  at  terminals  of 
4-ohm  sounder  in  circuit  with  the  cell  is  1.24. 

1.41X4h-1.24=4.5. 


4..") — !=..")  ohm,  internal  resistance  of  cell.  Care  must  be  tr.ken  to  read 
voltmeter  quickly  after  closing  the  circuit  through  coil,  or  the  result  will  be 
vitiated  by  the  polarization  of  the  cell. 

The  internal  resistance  of  a  dry  cell  can  al.so  be  determined  by  the  use  of 
the  voltammeter  previously  descrii)ed.  The  method  of  yroceilure  in  this  test 
is  as  follows : 

(391) 


12 


Signal  Corps  Manual  No.  3. — Chapter  9. 


Never  connect  with  more  than  one  storage  cell  or  more  than  three  of  other 
kinds.  Too  large  a  current  or  high  voltage  will  bend  the  indicator  or  burn 
out  the  coils. 

Dry  batteries  and  sal-ammoniac  batteries  (such  as  Leclanche,  donda.  etc.) 
should  have  voltages  between  1.4  and  1.5.  This  is  obtained  by  connecting 
with  binding  posts  V,  P  being  positive.  Then,  by  connecting  with  A  instead 
of  T.  the  current  is  indicated  on  the  ampere  scale.  Since  the  resistance  of  the 
ampere  coils  is  0..5  ohm.  the  internal  resistance  of  the  cell  is  given  by  the  for- 
mula   :^^        where  £'=voltage    of   the    cell   and    /=current   in    amperes.     The 

deterioration  of  a  dry  or  sal-ammoniac  battery  is  shown  by  a  fall  in  voltage 
much  below  1.4  and  a  rise  in  its  internal  resistance.  This  latter  should  not 
exceed  a  few  ohms. 

The  voltage  of  a  bluestone  cell  is  ordinarily  about  1.  Its  internal  resistance 
after  it  is  in  good  working  order  should  not  exceed  3  ohms. 

The  voltage  of  a  storage  cell  varies  between  l.S  when  al)out  discharged  to 
2.5  when  being  charged  fully.  After  charge  it  is  about  '1.  Tlie  internal 
resistance  should  be  very  small. 

Edison  primary  type  V  and  Gordon  cells  have  about  0.7.")  volt  E.  M.  F.  and 
internal  resistances  from  .06  to  .25  ohm. 

Fuller  cells  (with  electropoion  fluid)  have  from  LS  to  2  volts  E.  M.  F.  and 
an  internal  resistance  varying  from  one-fourth  to  one-half  ohm.  A  table  of 
internal  resistances  should  be  made  out  for  the  class  of  batteries  to  be  tested 
to  save  computations  in  making  the  round  of  inspections. 

In  this  connection  the  following  table  of  internal  resistance  is  supplied : 

Type  of  cell.  Ohms. 

Leclanche  and  Gonda 1.  50 

Samson .  25 

Gravity 3.  00 

Edison  primary  type  V  and  Gor- 
don       .  10 


Type  of  cell.  Ohms. 

4-0  dry 0.25 


4  dry___ 

5  dry___ 

6  dry._^ 

7  dry 

8  dry___ 


25 
20 
20 
12 
10 


Storage  cell .005 

Fuller ,  25 


THE    WHEATSTONE    KKIDGE. 

This  has  long  maintained  its  position  as  the  best  means  for  measuring  resist- 
ances, and  in  one  or  the  other  of  its  various  forms  can  be  used  for  a  great  range 
of  measurements. 


Fig.  9-15.— TEST,   OHMIC    RESISTANCE,    FALL  OF    POTENTIAL. 
(392) 


Miscellaneous  Tests  and  General  Information. — Chapter  9. 


13 


The  "  fall-of-potoutial  "  principle  is  applied,  wiiicli  may  be  illustrated  as 
follows  (fig.  9-15)  : 

If  a  current  is  tlowing  alonj;  a  wire  in  the  direction  ol'  .1  B,  and  the  ter- 
minals of  a  voltmeter  V  are  applied  at  -l  and  li,  a  certain  potential  difference 
between  these  points  will  be  indicated;  that  is,  there  will  be  a  fall  of  potential 
from  A  to  B,  which  will  be  miiform  if  the  wire  is  of  uniform  resistance.  This 
may  be  represented  jiraphically,  for  if  the  height  of  A  C  represents  the  total 
difference  of  potential,  and  the  line  C  li  represents  the  fall  of  this  to  B  along 
the  uniform  wire,  then  at  any  point,  say  at  E,  the  height  J>  E  will  represent 
the  potential  difference  between  H  and  E,  which  is  proportional  to  the  length 
of  wire  or  resistance  remaining. 

If  we  take  a  circuit  divided  at  A  (fig.  9-16),  the  fall  of  potential  along  the 
wire  .1  E  B  is  equal  to  that  along  the  wire  .1  G'  B,  and  having  passed  over  a 
certain  proportion  of  the  total  resistance  A  E  B  we  reach  a  point  E  which  will 
be  of  the  same  potential  as  some  jxtint  (!',  of  A  C!'  B.  If  E  and  G'  be  connected 
through  a  giilvanometi'r  no  current  will  flow  through  the  galvanometer.  It  can 
be  proven  that  when  the  resistances  of  the  divided  circuit  bear  the  proportion — 
A  E:A  G' :  :  E  B:G'  B — the  points  E  and  G'  are  at  the  same  potential  with 
respect  to  each  other,  and  the  galvanometer  will  not  be  deflected. 


Fig.  9-16.— TEST,    PRINCIPLE    EMPLOYED    IN    WHEATSTONE   BRIDGE. 

The  relation  of  parts  in  the  conventional  diagram  of  the  Wheatstone  bridge 
(fig.  9-17)  will  now  be  apparent.  If  the  resistance  in  the  coils  of  .1  and  B  are 
equal  or  bear  any  other  simple  numerical  relation,  then  the  same  numerical  rela- 
tion exists  between  R  and  -Y,  and  if  /?  be  a  box  of  known  resistance  coils, 
X,  the  unknown  resistance,  becomes  known  from  the  above-stated  relation 
A:B:  : R: X. 


Fig.  9-17.— TEST,  WHEATSTONE   BRIDGE,   CONVENTIONAL   DIAGRAM. 


(393) 


14 


Signal  Corps  Manual  No.  3. — Chapter  9. 


If  we  straighten  out  A  and  B  and  bend  up  A'  into  compact  form,  insert  keys 
into  tlie  galvanometer  and  battery  circuits,  we  shall  have,  the  diagram  of  the  or- 
dinary or  "post-office"  form  of  the  bridge  (fig.  9-18).  The  resistance  in  the 
"  balance  arm  "  A  and  B,  and  in  R  are  short-circuited  ))y  inserting  the  plugs, 
and  they  are  introduced  by  withdrawing  the  plugs.  The  galvanometer  now  most 
usually  employed  is  some  sensitive  form  of  the  suspended-coil  type. 


Fig.  9-18.— TEST,   WHEATSTONE    BRIDGE,    CIRCUITS,    DIAGRAMMATIC. 

The  simplest  measurement  is  made  with  A  and  B  equal.  Start  out  with,  say, 
A  and  B  100  ohms  each.  Then  connect  up  the  terminals  of  the  unknown  re- 
sistance X  ("line"  and  "ground"),  and  closing  the  battery  key,  tap  the  gal- 
vanometer key.  There  being  no  resistance  unplugged  in  R,  the  galvanometer 
needle  will  be  deflected  to  the  side  indicating  "  too  small"  for  R.  Now  unplug  in 
R  and  test  until  the  right  amount  is  unplugged  in  R  to  get  a  balance  or  no  de- 
flection, then,  since  A=B,  R—X.  If  fractional  ohms  are  to  be  obtained,  A 
must  be  10  or  100  times  greater  than  B;  then  R  is  10  or  100  times  greater  than 


Fig.  9-19. -TEST,    WHEATSTONE    BRIDGE,    POST-OFFICE   FORM. 

.V.  Likewise,  if  X  is  greater  liiaii  ciin  \iv  (>l)l:iiii(Ml  by  inipliigging  in  A',  tiien 
make  !{  llie  greater  and  it  r(>verses  (lie  nniltipiier.  Practice  and  care  are 
r('<niisit»'  to  obtain  acfurate  results.  Always  close  battery  key  befor<'  galvanom- 
eter key  Mild  njien  galvanometer  key  first.  / 


(.394) 


Miscellaneous  Tests  and  General  Information. — Chapter  9. 


15 


In  nieasurlnfr  resistances  of  n  tele.uraph  line  be  certain  all  line  batteries  are 
disconnected  before  inaliinji  tlie  measurement.  The  line  is  connected  with  one  of 
the  X  binding  posts,  tlie  ground  to  the  otiier.     (See  tig.  li-lS. ) 

Many  motlifications  of  tliis  form  of  bridge  are  in  u.se.  Some  are  arranged  so 
the  plugs  are  in.serted  at  the  points  where  the  introduction  of  resistance 
marked  Is  desired. 

One  of  the  familiar  forms  in  which  the  bridge  is  made  for  laboratory  use  is 
shown  in  figure  9-19.  In  this  the  resistances  are  introduced  by  taking  out 
plugs.  The  further  row  of  strips  are  for  the  .1  and  It  arms,  the  other  rows 
constituting  the  R  arm.  The  keys  are  for  introducing  battery  and  galvanometer 
into  circuit. 

The  following  gra])hical  demonstration  of  the  stated  i)roportiunality  of  the 
resistances  in  the  four  arms  of  the  Wheatstone  bridge  when  balance  is  obtained 
is  of  interest  in  connection  with  the  foregoing: 


/o/fs 

k 

x^ 

■  \ 

V 

^XZ7 

' 

- 

|\ 

\ 

A 

.  :^   , 

\l, 

\ 

/^ 


O^^nS 


Fig.  9-20.— TEST,   WHEATSTONE    BRIDGE.    GRAPHICAL    DEMONSTRATION. 


Lay  off  .1  U  to  represent  the  resistance  in  the  upper  lirancli  of  the  lu'idge 
(fig.  9-20)  and  A  F  to  repi'Psent  resistances  in  the  lower.  Let  A  C  represent 
the  difference  in  potential  bet\\"een  the  two  ends  of  the  bridge,  and  draw  lines 
C  B  and  C  F.  These  are  the  "  fall  of  potential  "  lines  along  the  upper  and 
lower  branches  I'esix'Ctlvely. 

A  horizontal  line  H  I)  touches  points  //  and  D  at  the  same  potential.  These 
l»ro.iected  on  lower  lines  represent  the  points  of  galvanometer  connection.  The 
resistances  passed  over  in  lower  and  upper  branches  to  reach  these  points  of 
equal  potential,  measured  on  the  lower  line,  are  .1  G  and  A  E. 

Similar  triangles  give  these  proportions : 


r   D:D    B: 
V  H:H  F. 

c  n-.n  B: 

A   E:E  B: 
A   E:A    G: 


:  .1  /;:  /;  n 

.A  G: G  F 
C  H:H  F 
A  G:G  F 
E  B:G   F 


F  and  li  being  at  the  same  point  in  the  convenrional  diagram  of  the  bridge 
(fig.  9-16).  the  last  proportion  will  be  seen  to  be  identical  with  that  accom- 
pijnying  that  figure. 

46581°— IT 26  (395) 


16  Signal  Corps  Manual  No.  3. — Chapter  9. 

The  wide  range  of  resistances  tlaat  can  be  measured  witli  a  Wlieatstone 
bridge  has  caused  it  to  be  liliened  to  a  pair  of  scales  whicli  may  be  converted 
from  hay  scales  to  a  chemical  balance.  It  has  been  noted  that  when  the 
"  balance  arms  "  are  equal  the  resistances  of  standard  coils  and  measured  re- 
.sistances  are  equal ;  and  by  changing  the  ratio  of  these  balance  arms,  which 
correspond  to  shifting  the  fulcrum  in  the  steelyard,  the  standard  resistance  may 
be  made  to  bear  any  desired  ratio  to  the  measured  i-esistance. 

VOLTAMMETER,     PORTABLE. 

Figure  9-21  shows  the  Weston  model  280  voltaunueter  which  is  issued  by  the 
Signal  Corps.  The  instrument  is  furnished  in  a  noat  leather  case  with  carrying 
strap  and  is  triple  range,  both  as  an  anuneter  and  as  a  voltmeter.  The  scale 
reading  as  an  annneter  being  0-3,  O-l-^,  and  0-30,  the  scale  readings  as  a 
voltmeter  are  0-3,  0-15,  and  0-150.  One  binding  post  is  conunon  for  l)oth 
ammeter  and  voltmeter  connection,  and  the  various  scale  connections  are  ob- 
tained by  connecting  other  lead  to  proper  one  of  six  other  binding  posts 
mounted  on  base  of  instrument.     All  binding  posts  are  appropriately  marked. 


Fig.  9-21. ^VOLTAMMETER,    PORTABLE. 

JlETIIOl)    OF    LOCATING    lAll.T.S    IN     Mri.Tll'I.K    COA'DITTOK    CAIU.KS    Wmi    JlODKl,    ItlOt 

OHM  METER. 

Arrange  to  have  the  dislnni  (>nd  of  (lie  faulty  conductor  connected  to  n  sound 
conductor  in  tlic  same  cable.  Attach  tlie  faulty  conductor  to  i)ost  .\ ,  on  the 
(thmmetcr  and  the  sctund  conductor  to  post  Q.  See  that  the  varial)lt'  plug  is 
not  inserted  at  either  10  or  100.  Attach  a  ground  wire  to  X-.  Find  a  balance 
as  in  testing  for  copper  resistance.  If  the  reading,  in  scale  parts,  is  A  and  the 
length  of  the  cable,  in  feet,  is  L,  the  distance  to  the  fault  will  be  Ij  nniltii)lied 
by  2.1  divided  by  1,000.  These  values  hold  for  any  size  cal)ie  but  assume  that 
tiie  conduct(trs  used  are  of  tlic  same  gauge.  Tlic  connections  ;irc  shown  in 
ligure  !)  22. 

The  following  cxaniplc  will   indicate  llie  method  of  maUing  this  test  : 
Supi)ose  connections  have  been  made  as  above  and  the  stylus  is  at   l.'K)  on  the 
scale  when  a  bulauce  has  l)een  obtained.     Suppo.se  the  cable  to  be  G,000  feet 

(.396) 


Miscellaneous  Tests  and  General  Information. — Chapter  9. 


17 


long;    6,000   multiplied    by    300    will    equal    1,800,(K)0,    wliich    divided   by    1,000 
equals  1,800  feet,  the  distance  from  the  observer  to  the  fault. 


Fig.  9-22.— TEST,  OHMMETER,   LOCATION   OF  GROUNDS. 
LOCATION    OF   A   CROSS   BY    MEANS    OF   THE   VOLTMETER. 

In  general  the  resistance  of  the  wire  to  the  cross  and  through  the  point  of 
contact  (the  cross)  of  the  two  wires  is  small  compared  with  the  resistance  of 
the  voltmeter  itself.  The  following  method  depends  upon  the  approximate 
correctness  of  this  assumption.     The  connections  are  shown  in  figure  9-23. 

Cross 


''E 


Fig.  9-23.— TEST,  VOLTMETER,    LOCATION   OF  CROSSES. 
(397) 


18 


Signal  Corps  Manual  No.  3.— Chapter  9. 


One  of  the  wires  is  grounded  at  some  station  E  beyond  the  cross,  the  otlier 
being  opened  there.  The  line  battery  being  connected  iip  througli  a  Ivuown 
resistance,  R  (a  150-ohm  relay,  for  instance),  as  shown,  readings  are  taken 
of  the  voltmeter  T'  connected  as  shown  first  by  the  full  lines  and  second  as 
shown  by  dotted  lines. 

Calling  the  first  reading  ^'^  and  the  second  T'  and  R  l.")0  ohms,  the  resistance 

of  the  wire  X  to  the  cross  is  given  by  the  formula   X=~y2XR.'  and  if  the 

resistance  of  the  wire  per  mile  is  A  ohms,  the  number  of  miles  to  the  cross  is 

X  * 

given  by  2^- 

The  quick  readings  that  can  be  made  with  the  voltmeter  make  this  a  useful 
method  of  locating  swinging  crosses. 

The  importance  in  all  these  tests,  excepting  ohmmeter,  model  1904,  of  having 
some  standard  known  resistances  available  is  apparent.  Spare  relays  and 
sounders,  if  not  already  measured  up  accurately,  should  be  so  measured  up 
and  marked  at  the  first  opportunity  or  request  made  for  such  standardized 
coils.  So-called  150-ohm  relays  and  4-ohm  sounders  frequently  vary  5  per  cent 
from  their  stated  resistance  and  would  make  considerable  error  in  the  calcu- 
lated positions  of  faults  if  used  as  standards. 

EXPLORING   COIL. 

It  is  oftentimes  necessary  to  locate  a  ground  or  cross  in  cables  installed  in 
trenches  or  underground  conduit  where  standard  instruments  are  not  available. 
The  u.se  of  an  exploring  coil  in  such  cases  may  avoid  the  necessity  of  taking 
up  considerable  lengths  of  cable  and  opening  unnecessary  test  points. 


I  yeifphone  fUceiver 


Surfoce.qt..  earlfi 


^ 


>=i 


Cither  duct  or  trench 


^tmc/- — I 


\ean 


pH' 


c-onaucra-  Wvtzar 


Fig.  9-24.— TEST,    EXPLORING    COIL,    LOCATION    OF    GROUND. 

The  exploring  coil  may  be  nuide  as  follows:  Take  a  1-inch  thick  pine  board 
of  rectangular  shape,  1  foot  by  2  feet,  and  wind  around  its  out(>r  edge  as 
many  turns  of  insulated  wire  as  convenient.  This  wire  may  be  ccHton-covered 
magnet  wire,  N(».  18  gauge,  or  smaller.  In  jtlace  of  this  board  a  rectangular 
frame,  with  cliannel  cross  .sections,  nuiy  be  made.  To  use  the  exi>loring  coil,  a 
source  of  alternating  (»r  pulsating  current  is  Mpi)lied  lo  the  grounded  conductor. 
Tills  source  may  be  from  a  buzzer  and  imluclion  coil  connected  to  a  battery  of 
dry  cells,  a  30-volt  telephone  storage  ballery,  or  a  110-volt  power  circuit. 
The  exploring  coil,  with  terminals  connected  to  ;i  telei)hone  receiver,  is  now 
carried  along  the  route  of  the  cable,  being  held  as  \w,\r  the  ground  as  possible 
with  the  plane  of  the  coil  pnr;illel  with  the  ciihle  and  the  long  side  of  the  coil 
next   to  the  ground.     The  buzzer  should    he   licnrd    in    the   telephone  receiver 


(;i98) 


Miscellaneous  Tests  and  General  Information. — Chapter  9. 


19 


until  the  f,n(>umled  point  in  the  cable  has  been  passed,  when  the  sound  should 
cease  entirely  or  becon)e  much  weaker.  Tlie  exploring  coil  may  also  be  used 
for  identifying  cables  where  a  inunber  of  them  are  laid  in  a  common  trench. 
A  variable  current  is  sent  through  the  cable  to  be  identified  and  is  picked  up 
by  the  exploring  coil,  one  side  of  which  should  be  held  close  to  or  parallel 
witii  the  cable.    The  sh(»rt  end  of  the  coil  may  be  used  for  this  i)urpose. 

MIIKKAY   AM)   VAKLEY   LOOP  TESTS. 

The  preceding  sections  of  this  chapter  have  de.scribed  certain  methods  of 
testing,  entirely  qualitative  in  character,  as  well  as  standard  methods  for 
measuring  conductor  resistance,  electro.static  capacity,  and  insulation  i-esistance. 
In  addition  to  these  there  are  certain  quantitative  measurements  necessary  for 
the  location  of  faults  in  conductors,  which  will  now  be  briefly  described. 

These  tests  for  fault  location  consist  essentially  of  cases  of  the  application 
of  the  simple  methods  of  measurements  previously  described,  requiring  special 
connections  and  a  certain  amount  of  computation  from  observations.  It  should 
be  esi)ecially  noted,  however,  that  the  methods  of  fault  location  connnonly  used 
do  not  necessitate  special  ami  ciynipliculed  ajjparatus,  but  rather  the  appiicatidii 


Fig.  9-25.— TEST,    MURRAY    LOOP,    LOCATION    OF  GROUNDS. 

of  simple  methods  to  special  circuits  and  the  solution  of  elementary  formul??. 
Two  tests  most  generally  used  and  of  wide  application  are  the  Murray  loop 
test  and  the  Varley  loop  test.  The  Murray  loop  test  is  the  more  easily  made, 
but  is  of  less  general  ai)plication  than  the  Varley. 

The  Murray  loop  circuit  is  shown  in  figure  9-2."),  in  which  A  is  one  of  the 
arms  of  a  Wheatstone  bridge  and  R  the  adjustable  resistance.  G  is  a  gal- 
vanometer or  other  current  indicater.  C  ("  the  leads  from  bridge  to  conductors 
under  test,  b  the  faulty  wire,  a  a  good  wire  of  the  same  length  and  resistance. 
The  resi.stance  of  the  faulty  conductor,  from  the  point  of  test  to  the  fault  is 
denoted  as  x;  a  and  b  are  connected  at  distant  end  as  shown  ,the  leads  €  C 
should  be  carefully  measured,  if  their  length  and  resistance  are  not  negligible 
as  compareil  with  those  of  the  wires  a  and  b  and  the  values  recorded  for  use 

(399) 


20 


Signal  Corps  Mainual  No.  3. — Chapter  9. 


in  correcting  readings.     Wlien  the  resistance  R  is  so  adjusted  that  the  gal- 
vanometer is  not  deflected  the  distance  to  tlie  fault  is — 

_AL 

where  L  is  the  combined  length  of  a  and  h.    The  above  formula  assumes  that 
the  leads  are  negligible.    If  such  is  not  the  case,  the  formula  becomes — 


A+R 


-C. 


It  will  usually  be  practicable  to  make  the  leads  negligible  or  at  least  to 
have  C=C'.  It  is  to  be  particularly  noted  that  this  method  assumes  that  the 
good  and  bad  wires  are  of  equal  resistance.     It  is  advisable  in  each  case  to 


Fig.  9-26.— TEST,    MURRAY    LOOP,    LOCATION    OF  CROSSES. 

check  the  fault  location  obtained  by  the  above  circuit  by  reversing  the  wires 
a  and  b  and  making  a  second  location.  In  the  above  formula  A  and  R  are  in 
ohm,s,  all  other  quantities  in  units  of  length. 

For  locating  crossed  wires  the  circuit  of  figure  9-26  should  be  used.  It  will 
be  noted  that  the  connections  are  the  same  as  for  locating  grounds,  except  that 
the  battery  is  connected  to  one  of  the  pair  of  crossed  wires. 

The  Varley  loop  test,  while  not  so  simple  and  quickly  made  as  the  Murray 
test  described  above,  is  of  more  general  application  and  can  be  made  in  situ- 
ations where  the  Murray  test  can  not.  The  coniurtious  for  this  test  are  shown 
in  figure  9-27.  The  various  i)arts  of  the  circuit  are  given  the  same  letter  desig- 
nations as  for  the  Murray  test  of  figures  9-25  and  9-26. 

With  the  circuit  of  figure  9-27  adjust  the  variable  resistance  arm  R  of  the 
Wheatstone  bridge  until  the  galvanometer  is  not  deflected,  record  the  values 
«)f  A,  li,  and  R.  Now  disconnect  the  ground  from  battery  and  connect  as 
shown  by  dotted  line  and  measure  the  combined  resistance  of  the  leads  C  C 
and  the  two  conductors  a  h  in  series;  call  this  value  r.  Combining  the  results 
of  the  two  nieiisui'ciiieiits  taken  above,  the  resistance  of  the  conductor  from 
the  point  of  test  to  the  fault  is — 


Br- A  R 
''   A-^B 


(400) 


-c. 


Miscellaneous  Tests  and  General  Information. — Chapter  9. 


21 


Check  the  iiieiisureineiits  aii<l  caleiilations  obtained  by  the  alxivt-  profess 
by  reversiiifj  the  coiiiieetions  of  tlie  bridse  to  the  conductors  at  either  end 
of  the  leads  and  obtain  a  socoiid  set  of  I'eadings.     If  the  new  values  of  bridge 


Fig.  9-27.— TEST,    VARLEY    LOOP,    LOCATION    OF  GROUNDS. 

readings  be  designated  as  A',  B' ,  and  /?',  the  new  value  of  the  resistance  to 
the  fault  is — 

If  C  equal  the  total  resistance  of  the  bad  wire  the  distance  to  the  fault 

is  j;,L,    where  /.  is  the  total  length  of  the  wire.     The  check  measurements 

should  always  be  made  when  using  either  the  Varley  or  the  Murray  loop  test, 
as  the  time  and  labor  required  are  inconsiderable  and  the  certainty  of  location 
is  much  increased. 

For  crossed  wires  the  method  of  figure  9-28  should  be  used.  The  circuit,  it 
will  be  noted,  is  the  same  as  on  figure  9-27,  except  that  one  wire  of  the  crossed 
pair  is  used  to  replace  the  earth  connection. 

r.OCATTOX  OF  F.VT^T.TS  IX  TELEGRAPH  LINE;S. 

"  In  order  to  secure  the  best  possible  result  in  the  working  of  telegraph  line.? 
we  nmst  keep  down  the  resistance  of  the  conductor  in  the  circuit  and  increase 
the  resistance  of  the  insulator  to  the  greatest  possible  extent.  In  other  words, 
the  resistance  must  be  as  small  as  jiossible  in  the  route  we  wish  the  electric  cur- 
rent to  travel  and  as  great  as  possible  in  every  other  direction.  The  practical 
working  value  of  a  telegraph  line  is  the  margin  lietween  the  joint  resistance  of 
the  conductor  and  the  insulator  and  that  of  the  insulation  alone.  The  tension 
of  the  retracting  spring  of  the  relay  armature  when  upon  a  '  working  adjust- 
ment '  is  the  measure  of  this  margin  or  ililference.  It  is  evident  that  this  margin 
may  be  increased  in  two  ways,  viz  :  (1)  By  increasing  the  insulation  resistance  : 
(2)  by  decreasing  the  resistance  of  the  conductor." — Pope's  Modern  Practice  of 
Electric  Telegraph. 

(401) 


90 


Signal  Corps  Manual  No.  3. — Chapter  9. 


Faults  causing  departure  from  normal  working  conditions  are  due  to  partial 
or  complete  contacts  of  the  line  wire,  directly  or  indirectly  with  the  ground, 


Fig.  9-28.— TEST,    VARLEY    LOOP,    LOCATION    OF  CROSSES. 

usually  called  i>y  telegraphers  "  escapes  "  and  "  grounds  " ;  crosses,  caused  by 
two  or  more  wires  coming  together ;  and  partial  or  complete  disconnections, 
causing  abnormally  high  resistance,  or  complete  interruption. 

"  Escapes  "  mean  imperfect  insulation,  due  to  defective  insulators,  contact  of 
foliage  with  the  wire,  or  defective  office  wiring.  "  Grounds  "  are  often  brought 
about  by  the  wire  being  down  on  the  ground,  to  its  being  detached  from  an 
insulator  and  lying  against  an  iron  pole,  or  defective  office  wiring. 

Abnormally  high  resistance  is  due  to  defective  and  corroded  joints  in  the  line 
wire  or  to  bad  connections  in  the  office  wiring,  instruments,  batteries,  or  grounds. 

When  stations  are  not  very  far  apart,  especially  where  they  are  along  a  rail- 
road or  good  road,  the  location  of  the  fault  between  two  stations  by  calling  up 
each  station  in  succession  is  usually  sufficient. 

In  case  of  escapes  it  is  evident  that  opening  the  key  beyond  the  escape  will 
not  entirely  open  the  circuit  at  the  testing  office  where  the  main-line  battery 
Is  located.  So  by  opening  in  succes.sion,  beginning  at  distant  stations,  until  we 
come  to  a  station  where  practically  all  current  cea.ses  when  the  key  is  opened, 
will  indicate  that  we  have  pas.sed  the  escape. 

The  inability  to  work  beyoml  a  given  station  indicates  a  "dead  gr<mn<l." 

Total  breaks  are  located  by  stations  successively  grounding,  beginning  :it  the 
nearest  oflice  to  the  testing  office. 

High  resistances  due  to  imperfect  connections  are  located  by  successive 
grounding  In  a  .similar  way,  a  sudden  marked  falling  off  in  strength  of  current 
indicating  that  the  high  resistance  has  just  been  passed. 

In  the  case  of  crosses  an  intermediate  ollice  is  asked  to  open  No.  1  of  the 
crossed  wires  and  work  on  No.  2.  If  upon  ()p(Mnng  No.  2  at  the  testing  office 
tlu'  cro.ss  remains,  as  shown  by  distant  stations'  sending  coming  in  on  N(».  1. 
it  is  evident  that  the  cross  is  Ix'tween  the  testing  oflice  iind  the  intcnnediiitc  one. 
If  tiic  cross  li:id  dis.-iitpcnred  upon  oi)ening  No.  1  at  the  interniediMtc  office  it  is 
lieyotid   tlic  intermediate  office 

In  llie  first  case  the  office  next  nearest  the  testing  oflice  is  called  and  the  test 
repeated   tliere.     In  the  second  case  we  should  proceed  outward  from  the  in 

(402) 


Miscellaneous  Tests  and  General  information.— Chapter  9. 


23 


terinediato  otfico.  A  iin'tallic  cross  may  he  distinguished  from  a  leakage  or 
"weather  cross"  i)y  the  sending  through  the  cross  in  the  first  case  coming 
nearly  as  strong  as  it  does  on  its  own  wire. 

If  a  high  resistance  fault  is  due  to  hatl  ofhce  connection  it  can  he  detected  hy 
cutting  out  the  odices  in  succession  nntil  an  evident  improvement  is  noted  in 
working.  If  due  to  bad  joints  in  the  line  it  can  generally  he  detected  hy  ground- 
ing at  each  station  in  succession ;  hut  these  can  best  be  located  by  measurements 
of  resistances  from  point  to  point. 

Faulty  ground  plates  often  introduce  very  large  resistance  in  the  line.  Con- 
nections with  the.se  should  he  very  carefully  made.  Only  soldere<l  joints  should 
he  permitted,  if  possible,  and  a  good-sized  rod.  plate,  or  a  good  length  of  coiled 
wire  buried  in  thoroughly  damp  ground  should  he  used.  It  has  often  been 
found  that  the  resistance  of  the  ground  connection  was  as  much  as  all  the  rest 
of  the  circuit. 

Two  lines  connected  with  a  bad  ground  jilate  will  behave  as  if  crossed. 

T.OCATTON  OF  CKOSSKS  OK  TEAKS  TX  TKI.KC.KAPIT  LINES  BY  MKANS  OF  THK  WIKK  RRIDOF,. 


For  crofmoi  (see  fig.  9-29)  :  Tall  crossed  lines  No.  1  and  No.  2.  Request 
rerniinal  station  or  any  station  beyond  cross  to  open  No.  1  and  ground  No.  2 
as  in  diagram.  The  distance  to  this  station  is  L  miles.  Connect  to  bridge 
consisting  of  a  resistance  wire  stretched  over  a  scale  of  100  equal  parts, 
galvanometer  and  battery  as  shown.     Call  divisions  of  wire  when  balance  is 


obtained  A  and  B. 


T> 

Tlie  distance  to  cross  X=— —L. 
100 


Fig.  9-29.— TEST,    IMPROVISED    BRIDGE,    LOCATION    OF    CROSSES. 

Proof:    A:B::L-X:X 
AX=BL-BX 

X(A+B)=BL;        X= 

A+B=100   .-.   X=Al 
100 


A-fB 


For  leaks  (see  fig.  9-30)  :  Suppose  No.  1  has  an  escape  (leak)  at  point  indi- 
cated. Terminal  or  station  beyond  leak  connects  No.  1  and  No.  2,  and  the 
ronnections  are  made  as  shown,  for  wires  of  same  gauge  and  material. 


T— €V 


I  I  I  H  I  I  I  I  I 


I 

T 


Fig.  9-30.— TEST,    IMPROVISED    BRIDGE,    LOCATION    OF    GROUNDS. 

(403) 


24  Signal  Corps  Manual  No.  3. — Chapter  9. 

Then  if  terminal  station  is  L  miles  the  distance  to  the  leak  X  when  balance 

A 

IS  obtained  is  — -L  miles. 
60 

Proof:    A:B::X:L+(L-X) 
2AL-AX=BX 

X(A+B)=2AL;    X=^^A^L. 

A+B=100  .•.X=4l 

50 

Intermittent  or  swinging  escapes,  grounds,  and  crosses  are  exceedingly 
troublesome  to  locate.  They  often  require  accurate  and  prompt  measure- 
ments. The  Weston  voltmeter  and  milammeter  set  described,  being  capable 
of  almost  instantaneous  readings,  is  particularly  useful  in  this  kind  of  meas- 
urement. The  ohmmeter  measures  resistances  directly  and  almost  as  quickly. 
The  Wheatstone  bridge  gives  the  most  accurate  results,  but  considerable  skill 
and  experience  are  necessary  in  its  use. 

The  ohmmeter  and  Weston  set  will,  it  is  believed,  give  greatest  satisfaction 
in  ordinary  office  measurements  of  resistance.  The  voltammeter  has  the  ad- 
ditional advantage  of  giving  means  for  measurements  of  voltage  and  current 
as  well. 

The  ohmmeter  furnishes  not  only  a  ready  means  of  measuring  resistance, 
hut  lends  itself  to  loop  tests  as  well. 

Where  only  one  wire  connects  the  stations,  grounds  or  escapes  may  he  ap- 
proximately located  by  the  ammeter  or  voltmeter  as  previously  stated. 

No  very  satisfactory  simple  methods  exist  for  locating  escapes  when  only 
the  faulty  wire  is  available,  and  the  tests  can  be  made  at  one  end  only. 

The  simplest  one  is  the  Blavier  test.  This  consists  of  making  measurements 
of  resistance,  first  with  the  distant  end  grounded  and  next  with  the  distant 
end  open.  The  resistance  of  the  entire  line,  when  in  good  condition,  must  be 
known.     (See  fig.  9-31.) 

Suppose  measurements  are  made  from  A,  B  is  asked  to  open,  and  measure- 
ment is  made  from  A  through  wire  to  fault  and  through  fault.  Call  the  re- 
sistance ilA  ohms.     B  then  closes  and  another  measurement  is  made.     Call  this 


Fig.  9-31.— TEST,  BLAVIER,    LOCATION   OF  GROUNDS. 

A'  ohms.     If  the  resistance  of  llic  line  is  />  when  in  good  condition,  the  resist- 
ance ill  (ihiiis  A    III  ilic  Caull   will  then  be  given  by  the  formula: 

X  =  N- ^(T^N)  (M-N). 

A  number  of  jiairs  nf  n>jidings,  using  each  «'iid  of  the  battery,  if  possible, 
shouhl  be  made,  and  the  mean  of  tho.se  pairs  that  agree  most  nearly  should 
be  taken. 

(404) 


Miscellaneous  Tests  and  General  Information. — Chapter  9. 


25 


Tha  ohmmeter  or  Weston  sot  may  ho  iisod  to  advantage  in  these  measure- 
ments and  readings  <tl)tained  as  quiclviy  as  possible  when  tlie  l)atlory  oiirront 
is  tlirown  on,  as  the  resistance  may  vary  rapidly,  due  to  the  polarization  at 
the  fault.  It  is  an  advantage  to  have  tlie  current  through  the  escape  'A 
the  same  when  measuring  .1/  and  'N .  As  a  rough  compensation  in  land  line 
moasuromont,  use  double  tho  battery  in  measuring  .V  as  when  J/  is  measured. 

KAUI.TKINDEH. 

An  instrument  termed  by  its  manuracturor  "  Faulttinder  "  is  issued  in  special 
instances  by  the  Signal  Corps. 

Tho  following  is  an  extract  from  a  catalogue  relating  to  the  faultfinder : 

This  instrument  has  lioon  designed  with  a  view  of  reducing  to  a  minimum,  cal- 
culations coniioctod  with  fault  location,  also  to  simplify  manipidation  as  much 
as  possible.  It  may  l)o  used  to  me.isuro  conductor  resistance,  to  measure  fault 
resistance,  to  locate  faults  by  four  different  tests,  and  when  used  with  a  buzzer 
and  telephone,  to  locale  opens. 

Full  directions  concerning  the  use  of  this  instrument  are  framed  on  the 
inside  of  cover.  A  special  battery  wliich  Is  supported  in  boiiom  oi  c'ase  is 
necessary  for  its  operation. 

Figure  9-32  shows  tbi'  faidttinder  with  cover  raised. 


Fig.  9-32.— FAULTFINDER. 


LINES     OK     INFORMATION. 


This  general  term  has  been  adopted  to  apply  to  the  means  by  which  military 
messages  are  transmitted  between  two  or  more  stations. 

Under  modern  conditions  lines  of  information  are  nearly  always  operated 
electrically.  On  account  of  its  certainty,  secrecy,  and  speed,  telegraphy  over 
wire  lines  is  to-day  without  a  rival  for  use  on  military  as  well  as  connnercial 
lines. 

As  an  army  advances  into  conquered  territory  it  will  utilize  as  far  as  pos- 
sible existing  commercial  lines  to  connect  it  with  its  base.     If  lines  are  con- 


(405) 


26  Signal  Corps  Manual  No.  3. — Chapter  9. 

structed,  they  will  generally  at  first  consist  of  the  insulated  wires  laid  on  the 
ground  which  follow  the  advance.  Such  of  these  as  are  needed  will  subse- 
quently be  put  up  as  light  lines  on  lances,  afterward  to  be  converted  into  perma- 
nent pole  lines  where  necessary.  Lines  of  a  temporary  character  will  be  con- 
structed or  laid  connecting  the  camps.  When  the  army  goes  into  action,  an 
important  series  of  lines  are  required  connecting  the  commanding  general,  the 
corps,  division,  and  brigade  commanders,  the  artillery,  and  probably  important 
points  of  observation  and  control  at  other  places  on  the  line. 

Classified  as  to  their  construction,  lines  of  information  are  permanent,  semi- 
permanent, or  field  lines. 

Permanent  lines  are  those  similar  in  construction  to  the  standard  telegraph 
lines,  and  usually  consist  of  heavy,  bare  copper  or  galvanized  iron  wire.  No.  9 
galvanized  wire  is  the  standard  in  our  service.  These  wires  are  supported  on 
substantial  insulators  and  strong  poles.  Such  lines  are  generally  operated  with 
the  standard  relays  and  sounders  familiar  in  commercial  offices. 

Semipermanent  lines  consist  of  lighter  bare  wires,  usually  No.  14  galvanized, 
supported  on  lighter  poles  called  lances,  or  on  light  tubular  steel  poles.  These 
lances  are  fitted  with  hard  rubber  or  composition  insulators.  Lines  such  as 
these  were  formerly  the  standard  military  construction,  and  telegraph  trains, 
consisting  of  wire  wagons,  battery  wagons,  and  lance  trucks,  could  construct 
from  7  to  15  miles  of  these  lines  a  day,  depending  on  conditions.  These  lines 
were  generally  operated  with  ])o\  relays,  but  in  modern  use  the  telephone  would 
frequently  be  the  instrument  employed. 

Field  lines  are  those  laid  hastily  for  temporary  use,  and  usually  consist  of 
insulated  wire  paid  out  from  reels  on  carts  or  wagons  or  in  the  smaller  size 
wire  from  hand  reels  or  wire  carriers.  Sometimes  bare  wire  is  used,  in  which 
ca.se  only  the  "  buzzer "  will  operate  satisfactorily  over  them.  This  buzzer 
is  generally  used  on  all  field  lines,  although  the  field  induction  telegraph  set 
may  be  substituted  for  it  under  some  conditions. 

Classified  in  regard  to  their  use,  lines  of  infonuation  may  be  considered  as 
either  strategical  or  tactical  lines. 

Strategical  lines  are  usually  of  the  permanent  or  semipermanent  character, 
and  may  be  part  of  the  commercial  system  of  the  country.  They  are  "  base 
lines  "  in  general,  as  they  lie  behind  the  advancing  army  and  maintain  com- 
nmnication  with  the  base  and  thence  to  the  seat  of  government.  On  account 
of  their  importance  they  would  frequently  be  duplicated,  and  in  general  over 
different  routes,  to  insure  connnunication  imder  all  conditions.  They  would 
in  some  cases  include  important  subiiuirine  cables.'  or  even  large  wireless 
stations. 

Tactical  lines  are  generally  of  the  field  line  class  and  are  rapidly  laid  or 
taken  up  to  follow  the  movements  of  the  units  they,  connect.  Tiieir  name 
indicates  llieir  uses.  Tliey  are  the  "  c(tiiiltal  liu«'s"  wliicli  late  improvements 
in   wire,   Iransjiortiit  ioii,   .-ind   instrumenls  liave  made  jtossible. 

Ill:  1,1)     IKAXSeoHTAI'IOX. 

Til  additifni  to  wagons  and  j)acks  for  ordinary  transportation,  the  Signal 
Toips  lias  found  it  necessary  to  devise  some  special  veliicles  for  transporting 
and  laying  wire  and  carrying  sucii  einiiimieiil   as  wireless  sets,  lances,  etc. 

Tlie  Army  is  now  e(|uipped  witii  a  imiuitei-  of  etlicienl  wire  carts.  This  type 
of  cart  is  drawn  by  two  liorses  and  sui»iMirts  two  spools  which  are  rotated  by 
means  of  a  sfirockel   wheel  iiiid  cliaiii  retaled  by  the  wheels  of  the  cart.     Each 

(400) 


Miscellaneous  Tests  and  General  Information. — Chapter  9.  27 

of  the  reel-s  of  this  cart  will  hold  i^i  luilcs  of  held  wire  and  a  lino  fan  ho  laid 
as  rapidly  as  the  horses  are  made  to  travel.  The  line  is  paid  out  from  the 
reel  on  the  j^round  and  is  laid  to  one  side  of  the  road  by  a  man  on  horseback 
in  rear,  by  means  of  the  wire  inkv.  descripetl  in  chapter  8. 

In  case  a  wire  cart  is  not  available,  held  wire  lines  may  be  laid  and  recov- 
ered by  means  of  quartermaster  escort  wagons  and  ordinary  take-uj)  or 
pay-out  reels. 

For  handling  the  small  insulated  buzzer  wire,  which  is  furnished  on  one- 
iialf  mile  spools,  the  wire  carriei-  and  iiand  reel  answer  every  purpose  either 
on  foot  or  mounted. 

The  instrument  wagons  are  either  spring  wagons,  or  the  regular  Army 
escort  wagon,  provided  with  paulins  or  wagon  covers,  in  which  instruments, 
light    tools,    repair    parts,    etc.,    may    be    transpoi-ted. 

The  lance  truck  is  a  wagon  with  a  high  seat  and  long  reafh,  sailed  for  the 
transportation  of  lance  poles.  I'our  mules  suffice  for  this  load  uiidt-r  ordinary 
conditions. 

Special  pack  chests  ai'e  provided  for  the  Signal  Corps  supplies,  and  the 
present  field  wireless  pack  set,  which  is  carried  on  three  mules,  requires 
special  fittings  for  the  aparejos. 

WIKE   USED   IN    FIELD   OPERATION'S. 

For  the  permanent  military  lines,  No.  9  galvanized  wire,  weighing  820  pounds 
to  the  mile,  is  the  standard. 

For  semipermanent  lines,  such  as  lance  lines,  No.  14  galvanized  wire,  weigh- 
ing about  100  pounds  per  mile,  is  used. 

The  two  kinrls  of  wire  used  in  field  lines  are  known,  respectively,  as  "  field 
wire  "  and  "  buzzer  wire."  The  former  corresponds  with  the  "  field  cable  "  used 
abroad.  Our  field  wire,  described  in  chapter  8  of  this  manual,  has  a  tensile 
strength  of  over  300  pounds  and  weighs  70  pounds  per  mile.  Five  miles  of  it 
may  be  carried  on  the  drums  of  the  latest  type  wire  cart.  Its  strength  and 
insulation  are  little  impaired  by  wagons  and  troops  passing  over  it.  It  is  very 
pliable  and  lies  flat  on  irregular  ground.  As  it  is  laid,  mounted  men  follow 
the  reel  cart  with  pikes  or  lances  luiving  hooks  on  the  ends,  either  placing  the 
wire  out  of  the  way  on  the  road,  or  if  need  be,  hooking  it  up  on  trees.  It  is 
difficult  to  break  or  injure  this  wire  unintentionally.  If  found  broken,  a  tem- 
porary splice  should  be  made.  This  is  done  by  tying  the  ends  together  with 
a  hard  knot,  leaving  about  a  foot  of  each  free.  The  insulation  is  then  removed 
from  the  ends  for  several  inches  and  the  bare  wires  twisted  together. 

Buzzers  or  camp  telephones  may  be  quickly  connected  to  field  wire  by  means 
of  "  Type  A  buzzer  connectors."  These  connectors  are  furnished  with  sharp 
teeth  that  pierce  the  insulation  readily  and,  when  withdrawn,  damage  the 
wire  very  little. 

In  every  way  this  type  of  wire  seems  eminently  suited  for  field  lines,  the 
only  objection  being  its  cost,  which  is  about  $75  per  mile. 

A  small  wire  of  this  class,  suitable  for  laying  from  a  hand  reel,  is  called 
"  buzzer  wire,"  described  in  chapter  8  of  this  manual.  This  wire  weighs 
about  10  pounds  per  mile  and  is  put  up  on  half-mile  spools.  This  permits 
[laying  out  tlu'  wire  from  a  sinqile  holder  from  horseback  and  its  recovery  by 
means  of  a  hand  reel.  This  wire  is  used  for  short  lines  or  for  emergency  lines 
over  rough  ground  where  the  heavier  lield  wire  can  not  be  carried. 


(407) 


28  Signal  Corps  Manual  No.  3.— Chapter  9. 

It  may  be  useful  to  remember  that  since  buzzers  will  operate  over  long 
stretches  of  bare  wire  laid  on  the  ground  even  in  wet  weather,  field  lines  of 
any  kind  of  wire  available  may  be  laid  in  emergencies. 

INSTRUMENTS    FOR    ELECTRICAL    LINES    OF    INFORMATION. 

Base  lines  and  other  permanent  telegraph  lines  will,  of  course,  make  use  of 
the  familiar  commercial  apparatus.  Morse  instruments  of  various  portable 
forms,  such  as  the  box  relay,  main-line  sounder,  or  pocket  relay,  >vill  be  used 
on  semipermanent  lines  wherever  practicable.  These  require,  however,  large 
battery  equipment  and  well-insulated  lines,  and  in  bad  weather  the  instruments 
are  difficult  to  keep  in  adjustment. 

THE    BUZZER. 

On  our  field  lines  the  buzzer  in  one  of  its  forms  is  almost  universally  used. 
This  instrument  was  introduced  into  our  service  about  1890  and  first  showed  its 
capabilities  in  the  Pliilippine  and  China  campaigns.  In  its  present  form  of 
"  service  buzzer  "  it  combines  a  complete  telegraph  and  telephone  station,  includ- 
ing the  necessary  batteries.  Its  capacity  for  working  over  circuits  impossible 
for  any  other  telegraph  instruments,  such  as  bare-wire  lines  laid  on  the  ground, 
through  wire  of  wire  fences,  or  railroad  rails,  or,  more  incredible  still,  through 
consideralile  breaks  in  tlie  line  wlien  the  ends  lie  on  the  ground,  makes  it  the 
ideal  instrument  for  field  lines. 

To  open  a  station  it  is  only  necessary  to  fasten  the  buzzer  connector  with 
flexible  cord  from  one  binding  post  to  the  field  wire,  and  from  the  other  binding 
post  a  flexible  wire  leads  to  a  small  ground  rod  or  metal  peg  driven  into  the 
ground. 

By  working  the  key  an  interrupter  is  operated  giving  a  higli  singing  note, 
which  is  i)roken  up  into  the  dots  and  dashes  of  the  Morse  alphabet.  These 
correspond  to  vil)ratory  electrical  impulses  which  go  out  on  the  line  and  are 
heard  in  the  teloplione  receiver  at  the  distant  station.  The  efficiency  of  the 
buzzer  under  the  difficult  conditions  stated  is  due  to  the  marvelous  sensitiveness 
of  the  telephone  receiver  to  these  rapidly  pulsiiting  currents.  In  practically  the 
same  circuit  as  the  interrupter  is  a  telephone  transmitter,  and  when  the  button 
switch  on  this  is  depressed  the  instrument  becomes  at  once  converted  into  a 
very  efficient  telephone  set. 

THE    CAMI-    TELEI'HONE. 

This  instrument  described  in  chapter  3  lias  all  the  component  parts  of  the 
most  complete  telephone.  The  box  is  very  strong  and  weatherproof  and  has  a 
strap  for  convenience  in  carrying.  The  connections  are  very  simple  and  easily 
rej)aired  when  deranged.  If  can  hv  connected  to  field  lines  and  the  ground  in 
the  same  way  as  the  b\r/>zer.  Its  common  use,  however,  is  for  cami)  lines  where, 
with  its  generator  and  call  bell,  it  is  .specially  suited  for  connection  with  the 
camp  switchboard  described   in  chapter  8. 

KIEI.l)     INDIICTION     TELEfJK.MMI. 

On  semipermanent  lines,  especially  where  business  over  them  is  heavy,  the 
continual  use  of  (lie  bnz/er  is  very  fatigin'ng  to  Morse  operators.  The  induction 
telegraph  sv\  desc  riixMl  in  ciiiipler  'J  li.-is  l)eeii  devised  especially  for  this  class 
of  lines,  operating  the  key  of  this  instrument  .sends  out  impulses  of  high  volt- 
age over  the  line  and  relays.    These  relays  are  very  sensitive  and  operate  with 

(408) 


Miscellaneous  Tests  and  General  Information. — Chapter  9.  29 

a  remarkably  small  ruriiMit.  As  a  result  of  the  voltaRO  increase  and  relay 
sensibility,  three  dry  cells  of  battery  will  work  the  sets  over  Inindreds  of  miles 
of  iron  wire,  over  ordinary  circuits  where  the  insulation  Icnkaw  permits  the 
escape  of  On  per  cent  of  the  current.  Doing  away,  as  it  does,  with  carryint;  large 
amounts  of  battery,  it  is  believed  to  be  a  useful  intermediate  instrument  be- 
tween the  buzzer  and  the  regular  telegraph  installation. 

SKLECTION    OF   INSTRUMENTS. 

The  buzzer,  the  telephone,  and  telegraph  each  has  fairly  well  defined  roles  in 
operating  electrical  lines  of  information.  The  buzzer  is  the  pioneer  which  clears 
the  way,  follows  up  the  fighting  line,  and  can  operate  over  any  kind  of  a  line. 
Its  function  as  a  telegraph  instrument  is  the  paramount  one  on  account  of  its 
reliability,  although,  as  stated,  it  is  a  good  telephone  when  the  wire  is  in  proper 
condition.  The  camp  teleplione  is  most  useful  in  camp  administration  lines  or 
over  semipermanent  lines  in  general  where  telephone  service  seems  desirable. 

The  telegraph  is  standard  where  lines  are  established  and  where  the  volume 
and  importance  of  business  become  great.  To  the  trained  operator  there  is 
nothing  to  equal  the  clearness  and  certainty  with  which  a  message  on  a  Morse 
sounder  is  delivered,  and  such  operation  is  the  ultimate  excellence  toward  which 
military  lines  aim. 

The  decision  as  to  when  the  telephone  or  telegraph  should  be  installed  or  used 
is  governed  by  the  following  considerations : 

The  telephone  does  not  require  trained  operators. 

The  telephone  may  be  used  for  direct,  and  consequently  confident inl.  com- 
munication between  officers. 

Time  is  saved,  compared  with  telegraphy,  especially  when  the  users  are  accus- 
tomed to  the  telephone. 

The  telegraph  is  superior  to  the  telephone  in  the  following  ways : 

Accuracy. — A  written  message,  spelled  out  by  telegraphy,  written  and  de- 
livered, has  an  obvious  advantage  over  one  delivered  by  word  of  mouth. 

licUnhiUfy. — In  the  field,  especially  when  the  wind  is  blowing  in  the  ears  and 
viirious  other  noises  tend  to  confuse,  it  is  very  hard  to  distinguish  in  the  tel- 
ephone words  which  sound  alike.  This  is  especially  confusing  to  an  enlisted 
man  unused  to  expressions  conunon  in  military  messages.  The  sharp  signals  on 
the  buzzer  or  sounder  are  nmch  more  reliable. 

Speed. — It  is  found  in  the  case  of  written  messages  transmitted  by  buzzer  and 
telephone  that,  owing  to  frequent  repetitions  required  by  telephone,  the  buzzer 
will  generally  exceed  it  in  speed. 

From  the  foregoing  considerations  it  is  evident  that  officers  should,  when 
time  permits,  always  write  out  their  messages  in  proper  form.  The  use  of  the 
telephone- should  be  restricted  to  conminnication  between  officers.  The  direction 
to  an  operator  verbally  to  send  messages  liy  telegraph  is  inadvisable.  Sending 
messages  by  dictation  through  the  telephone  invites  almost  certain  errors. 

Miscellaneous  Tables  and  Information. 

t'nits  of  resistance. 

Th<>  unit  of  n>sistan«t'  now  universally  used  is  the  international  ohm.  Tlie 
following  multiples  of  this  unit  are  sometimes  employed: 

Ohms. 
Megohm =1,000,000. 
Microhm =0.000,001. 

(409) 


30 


Signal  Corps  Manual  No.  3. — Chapter  9. 


The  following  table  gives  the  value  of  the  principal  practical  units  of  resist- 
ance which  existed  previous  to  the  establishment  of  the  international  iniits; 


Unit. 

Interna- 
tional ohm. 

B.A.ohm. 

Legal  ohm, 

1884. 

Siemens' 
ohm. 

1.000 
.9866 
.9972 
.9407 

1.0136 
1.000 
1.0107 
.9535 

1.0028 

.9894 
1.000 
.9434 

1.06.30 

B.  A.ohm  

1.0488 

1.0600 

1.000 

Then 


Thus,  to  reduce  British  Association  ohms  to  international  ohms  we  divide 
by  1.0136,  or  multiply  by  0.9866;  and  to  reduce  legal  ohms  to  international 
ohms  we  divide  by  1.0028,  or  multiply  by  0.0972,  etc. 

SPECIFIC   RESISTANCE. 

Let  Z=length  of  the  conductor. 

J.^cro.«:s  section  of  the  conductdr. 
i?=resistance  of  the  conductor. 
/)=specific  resistance  of  the  conductor. 

I 

'a' 

or  p=R^. 

If  I  is  measured  in  centimeters  and  -1  in  square  centimeters,  p  is  the  resist- 
ance of  a  centimeter  cube  of  the  conductor.  If  /  is  measured  in  inches  and  A 
is  .square  inches,  p  is  the  resistance  of  an  inch  cube  of  the  conductor. 

In  telegraph  and  telephone  practice,  specific  resistance  is  .sometimes  ex- 
pressed as  the  ivcifiht  per  mile-ohm,  which  is  the  weight  in  pounds  of  a  con- 
ductor 1  mile  long  having  a  resistance  of  1  ohm. 

Another  common  way  of  expressing  specific  resistance  is  in   terms  of  ohms 
per  mil- foot,  i.  e..  the  resistance  of  a  round  wire  1  foot  long  nnd  0.001   inch 
in  diameter;  /  is  then  measure<l  in  feet  and  A  in  circular  mils. 
Microhms  i)er  inch  cu]ie=0.r{!t;{7X microhms  per  ('(MUimeter  cube. 
Pounds  iier  mil(>-ohm  =  r)7.07X microhms  i)er  centimeter  cul)eX.si)ecitic  gravity. 
Ohms  per  mi]-foot=6.01.1X microhms  i»er  centimeter  cul)o. 
Specific  conductivity  is  the  reciprocal   of  specific  resistance.     If  r=specific 
condutivity, 

/ 

-cA' 

J_ 

'-RA' 


R= 


1 


I'.y  relative  or  pcrcontiige  conductivity  of  :i  siiiniil(>  is  inc.-int  100  times  the 
ratio  of  tiic  condnctivity  of  the  sample  ;it  standard  tenqu'rat  ur*'  to  the  con- 
ductivity of  a  conductor  of  the  same  dimensions  made  of  the  standard  ma- 
terial and  at  standard  tenq)erat\u-e.  If  p„  is  the  specific  resistance  of  the 
sample  at  standard  temperature  and  /).,  is  the  sijccific  resistance  of  the 
standard  at  stand;ird   lenqieriitiire,  then 

Percentage!  conducl  ivitv=100'''. 

Po 

(410) 


Miscellaneous  Tests  and  General  Information. — Chapter  9.  31 

In  coniparinj,'  different  materials,  the  specific  resistance  sliould  always  in; 
determined  at  the  standard  temperature,  whicli  is  usually  talien  as  0°  cen- 
tigrade. If  it  is  inconvenient  to  measure  the  resistance  of  the  sample  at 
the  standard  temperature,  this  may  he  readily  calculated  if  tlie  temperature 
coelHcient  n  of  the  sample  is  linown,  i.  e., 

Avliere  pt  is  the  specihc  resistance  at  teujperature  /. 

^latthiessen's  standard  of  conductivity,  winch  is  the  commercial  standard, 
is  a  copper  wire  haviiii:  the  followinir  properties  at  the  standard  temperature 
of  0°  centigrade : 

SpeciHc   gravity 8.89. 

Length ^ 1  meter. 

Weight 1  gram. 

Resistance 0. 1-11720  ohms. 

Specific  resistance l.oiM  microhms  per  cubic  centimeter. 

Relative  conductivity KTd  per  cent. 

i^pccific  rcsistuncv,  ninlirc  rrsit^finirr.  (iiid  rrldlirc  conductivity  of  coiirJurtors. 
[Roferred  to  Mattliicsseu's  standard.] 


Metals. 


Silver,  anne^nled 

Copper,  auiicalod 

Copper  ( Matthiessen's standard) 

Gold  (i)9.9  per  cent  pure) 

Aluminum  (99  per  cent  pure). . . 

Zinc 

Platinum,  aruiealed 

Iron 

Nickel 

Tin 

licad 

Antimony 

Mercury 

Bismuth 

Carbon  (graphitic) 

Carbon  (arc  light) 

Selenium 


Resistance  in  microhms 
at  0°  C. 


Centimeter 
cube. 


1.47 
1.5.5 
1.594 
2.20 
2.  .56 
5.  75 
8.98 
9.07 
12.  .3 
13.1 
20.4 
.^5.2 
94.3 
130. 
2,400-42,000 
about  4,000 
6X10>» 


Inch  cube. 


0.579 
.610 
.  6276 
.865 
1.01 
2.26 
3.53 
3.57 
4.&5 
5. 16 
8.04 
13.9 
37.1 
51.2 
950-16, 700 
about  1,.590 
2.38X1010 


Relative  ,  Relative 


resist- 
ance. 


Per  cent. 
92.5 
97.5 

100 

138 

161 

362 

.565 

570 

778 

S2S 
1.280 
2.210 
5. 930 
8,220 


conduc- 
tivity. 


Per  cnt. 
108.2 
102.6 
100. 
72.5 
62.1 
27.6 
17.7 
17.6 
12.9 
12.1 
7.82 
4.  .53 
1.69 
1.22 


Resistances  of  liquid  conductors. 


Liquids  at  18°  C. 


Pure  water 

Sea  water 

Sulphuric  acid: 

5  percent 

30  per  cent 

SO  per  cent 

Nitric  acid,  30  percent .. . 
Zinc  sulphate,  24  per  cent 


Ohms  per 

centimeter 

cube. 


2,650. 
30. 

4.86 
1.37 
9.18 
1.29 
21.4 


Ohms  per 
inch  cube. 


1,050. 
11.8 

1.93 
.544 

3.64 
.512 

8.54 


46581°— 17- 


(411) 


32 


Signal  Corps  Manual  No.  3. — Chapter  9. 


TEMPERATURE   COEFFICIENT. 

The  i-esistauce  of  ii  conductor  varies  with  the  temperature  of  the  couductor. 

Let  i?o=resistance  at  0°. 
R  =  resistance  at  i°. 
Then  7?  =Ro  (1+fl  O- 

a  is  called  the  temperature  coefficient  of  the  conductor;  100  a  is  the  percentage 
change  in  resistance  per  degree  change  in  temperature. 

The  following  values  of  temperature  coefficients  have  been  found  for  l(Mnpera- 
tures  measured  in  degrees  Centigrade  and  in  degrees  Fahrenheit.  It  is  to  be 
noted  that  the  coefficients  vary  considerably  with  the  purity  of  the  conductor. 


Pure  metals. 


Silver,  annealed 

Copper,  armealed 

Gold  (99.9  per  cent) 

Aluminum  (99  per  cent) 

Zinc 

Platinum,  annealed 

Iron 

Nickel 

Tin 

Lead 

Antimony 

Mercury 

Bismuth 


Centi- 

Fahren- 

grade.i 

heit. n 

0.00400 

0.00222 

.00428 

.00242 

. 00377 

.00210 

.  (XM23 

.00235 

. 00406 

.00226 

.00247 

.00137 

.00625 

.00347 

.0062 

.00345 

.00440 

.00245 

.00411 

.00228 

. 00389 

.00216 

.00072 

.00044 

.00354 

.00197 

Matthiessen's  formula  for  soft  copper  wire  R=Ro  (l+.00387*+.00000597f=). 

The  wire  used  by  Matthiessen  was  as  pure  as  could  be  obtained  at  the  time 
(1860),  but  in  reality  contained  considerable  impurities;  the  above  formula, 
therefore,  is  not  generally  applicable.  Later  experiments  have  shown  that  for 
all  practical  work  the  above  equation  for  copper  wire  may  be  written  R=Ro 
(1+.0042O  for  t  in  °  C. 

WIRE  GAUGES. 

The  sizes  of  wires  are  ordinarily  expressed  by  an  arbitrary  series  of  numbers. 
Unfortunately  there  are  several  independent  numbering  methods,  so  that  it  is 
always  necessary  to  specify  the  method  or  wire  gauge  used.  The  following  table 
gives  the  numbers  and  diameters  in  decimal  parts  of  an  inch  for  the  various 
wire  gauges  used  iu  this  country  and  England: 


(412) 


Miscellaneous  Tests  and  General  Information. — Chapter  9. 


33 


Number 
of  wire 
gauge. 

Roebling 
or  Wash- 
burn & 
Moens. 

Bro\TO  & 
Sharpe. 

BirminR- 
ham  or 
Stubs 

English  le- 
gal stand- 
ard. 

Old  Eng- 
lish or 
London. 

Inch. 

Inch. 

Inch. 

Inch. 

Inch. 

6-0 
5-0 
4-0 

0.  460 
.430 
.393 

0.464 
.4.32 
.400 

""6.'4606"' 

6.' 454" 

'"o.ihAo" 

3-0 

.362 

.4096 

.425 

.372 

.42.50 

2-0 

.331 

.3648 

.380 

.348 

.3800 

0 

.307 

.3249 

.340 

.324 

..3400 

1 

.283 

.  2893 

.300 

.300 

.3000 

2 

.263 

.  2576 

.284 

.276 

.2840 

3 

.244 

.2294 

.259 

.252 

.2.590 

i 

.225 

.  2043 

.2.38 

.232 

.2380 

5 

.207 

.1819 

.220 

.212 

.2200 

6 

.192 

.1620 

.203 

.192 

.  2030 

7 

.177 

.1443 

.180 

.176 

.1800 

S 

.  162 

.128,5 

.165 

.160 

.  16.50 

9 

.118 

.1144 

.148 

.144 

.1480 

10 

.  1M5 

.1019 

.134 

.128 

.1340 

11 

.120 

.00074 

.120 

.116 

.1200 

12 

.105 

.  08081 

.109 

.104 

.1090 

13 

.092 

.07196 

.095 

.092 

.09.50 

14 

.080 

. 06408 

.083 

.080 

.08.30 

15 

.072 

.  05706 

.072 

.072 

.0720 

16 

.063 

.05082 

.065 

.064 

.06.50 

17 

.054 

.04525 

.058 

.056 

.0.580 

18 

.047 

.04a30 

.049 

.048 

.0490 

19 

.041 

. 03589 

.042 

.040 

.0400 

20 

.  035 

.  03196 

.035 

.036 

.  03.50 

21 

.032 

.02846 

.032 

.032 

.a315 

22 

.028 

.  02.534 

.028 

.028 

.  0295 

23 

.025 

.  02257 

.025 

.024 

.0270 

24 

.023 

. 02010 

.022 

.022 

.  02.50 

25 

.020 

.01790 

.020 

.020 

.0230 

26 

.018 

.01594 

.018 

.018 

.  0205 

27 

.017 

.01419 

.016 

.0164 

. 01875 

2S 

.016 

.01264 

.014 

.0148 

.  016.50 

29 

.015 

.01125 

.013 

.0136 

.015.50 

30 

.014 

. 01002 

.012 

.0124 

. 01375 

31 

.  0135 

.  00893 

.010 

.0116 

. 01225 

32 

.0130 

. 00795 

.009 

.0108 

.01125 

33 

.0110 

.00708 

.008 

.0100 

.01025 

34 

.0100 

.00630 

.007 

.0092 

.0095 

35 

.0095 

.  00561 

.005 

.0084 

.0090 

36 

.0090 

.00500 

.om 

.0076 

.  0075 

37 
38 
39 
40 

.0085 
.0080 
.0075 
.0070 

. 00445 
.00397 
. 00353 
.00314 

.0068 
.0060 
.0052 
.0048 

.0065 
.0057 
.0050 
.0045 

Roehling  gauge. — Used  in  this  country  for  iron  and  steel  wire. 

Broum  d  Sharpe  gauge. — The  American  standard  for  copper  wires  for  elec- 
trical purposes. 

Birmingham  gauge. — Used  lariiel.v  in  England  and  also  in  this  country  for 
iron  and  steel  wires  for  electrical  purposes. 

LAW  OF  THE  BROWX   &   SHARPE  GAUGE. 

The  diameters  of  wires  on  the  B.  &  S.  gauge  are  obtained  from  the  geometric 
series  in  which  No.  0000=0.4600  inch  and  No.  36=0.005  inch,  the  nearest  fourth 
significant  figure  being  retained  in  the  areas  and  diameters  so  deduced. 

Let       n  =  gauge  number  (0000  =—3;  000  =  —  2;  00=-l). 
d  =  diameter  of  wire  in  inches. 


Then  d-- 


0.3249 
'1.123"* 


(413) 


34 


Signal  Corps  Manual  No.  3. — Chapter  9. 


Sheathing  core. — The  number  (N)  of  sheathing  wires  having  a  tliauieter  (d) 
which  will  cover  a  core  having  a  diameter  (/>)  is 


iV=7r 


D+d 


Tensile  strength  of  copper  irire. 

COMMERCIAL  STANDARDS. 


Kumbers, 
B.  &S. 
gauge. 

Breaking  weight. 

Numbers, 
B.  &S. 
gauge. 

Breaking  weight. 

Hard- 
drawn. 

Annealed. 

Hard- 
drawn. 

Annealed. 

(MKX) 
000 
00 
0 
1 
2 
3 
4 
5 
6 

8 

Poundn. 
8.310 
6. 580 
5.226 
4.. 558 
3,746 
3,127 
2,480 
1,967 
1.559 
1.2.37 
980 
778 

Pounds. 

5, 6.50 

4.480 

3.  ,553 

2, 818 

2,234 

1,772 

1,405 

1,114 

8.83 

700 

555 

440 

9 
10 
11 
12 
13 
14 
15 
16 
17 
18 
19 
20 

Pounds. 

617 

4S9 

388 

307 

244 

193 

153 

133 

97 

77 

61 

48 

Pounds. 

349 

277 

219 

174 

138 

109 

87 

69 

55 

43 

34 

27 

The  stnnigth  of  soft  copper  wire  varie.s  from  ;«.0()0  to  ;}6,()00  pounds  per 
square  inch,  and  of  hard  coi)i)er  wire  from  45,0tl()  to  6S,(KK)  pounds  per  square 
inch,  according  to  the  degree  of  hardness. 

The  above  table  is  calculated  for  34,00t)  pounds  for  soft  wire  and  (JO.OOO 
pounds  for  hard  wire,  except  for  some  of  the  larger  sizes,  where  the  breaking 
weight  per  scjuare  inch  is  taken  at  50,000  pounds  for  0000,  000,  and  00;  55,000 
for  0 ;  and  57,000  pounds  for  1. 

Hard-draini  copper  telephone  and  teleyrapli  ivire. 

COMMERCIAL    VALUES. 


Size 
B.  &S. 

guage. 

Kesistaiipe 
per  mile. 

Breaking 

utrenjjth. 

Weight 
per  mile. 

Furnished 

in  coils  as 

follows. 

Approximate  size 
Vj.  R.  H.  iron  wire 
equal  to  copper. 

Ohw.i. 

Poundn. 

Pounds. 

Miles. 

'.) 

4.30 

625 

209 

1 

2 

10 

.5.40 

525 

166 

1.2 

3 

11 

6.00 

420 

131 

..52 

4 

12 

8.70 

330 

104 

.65 

6 

Iron  -  wire 

13 

10.90 

270 

83 

1.20 

61 

gua,i;e. 

14 

13.  70 

213 

66 

1.50 

8 

15 

17.40 

170 

52 

2.(X) 

9 

16 

22.10 

130 

41 

1.20 

10 

ill  liMiidling  this  wire  t]i<'  greatest  r;\rv  siiould  lie  oliserved  to  avoid  kinks, 
i)ends,  scratclies,  or  cuts.  .loiiits  should  he  made  only  with  copiier  s])]icing 
sleeves  and  connect  oi-s. 

On  account  of  its  conductivity  being  about  live  times  that  of  Ex.  B.  B.  iron 
wire,  and  Its  l)reaking  strength  over  three  times  its  weight  per  mile,  copper 
may  be  used  of  which  the  section  is  smaller  and  the  weight  less  than  an 
('((uivalent  iron  wire,  allowing  a  greater  minilier  of  wires  to  lie  strung  on  the 
poles. 


(414) 


Miscellaneous  Tests  and  General  Information. — Chapter  9. 


35 


Besides  this  advantage,  tlie  reduction  of  section  materially  decreases  tlie 
electrostatic  capacity,  while  its  nonmagnetic  character  lessens  the  self-induction 
of  the  line,  Ixttli  of  which  features  tend  to  increase  the  possible  si)eed  of  sig- 
naling in  tek'graphing,  and  to  give  greater  clearness  of  enunciation  over 
telephone  lines,  especially  those  of  great  lengtli. 


Standard  copper  strands. 

rOMMKUCIAT.    STANUAKUS. 


Wires. 

1 

C.  M. 

Outside 

Weight  per 
1,000  feet. 

diameter. 

Xumber. 

Size. 

Inch. 

Inches. 

Pounds. 

2,000,000 

127 

0. 1255 

1.632 

6,100 

1,950,000 

127 

.  1239 

1.611 

5,948 

1,900,000 

127 

.1223 

1.590 

5, 795 

1,8.')0,(K)0 

127 

.  1207 

1.  .569 

5,643 

1,SOO,IM)() 

127 

.1191 

1.548 

5,490 

1,7.')0,IXH) 

127 

.1174 

1.  526 

5,338 

1,7U0,0(_K) 

91 

.1367 

1.504 

5, 185 

l,f):>l),lKK) 

91 

.  1347 

1.482 

.5,033 

1,000,000 

91 

.  1326 

1.459 

4,8M) 

1,0.30,000 

91 

.  1305 

1.436 

4,728 

1,500,000 

91 

.1284 

1.412 

4,575 

1,4.")0,000 

91 

.  1262 

1.388 

4,423 

1,400,000 

91 

.1240 

1.364 

4,270 

1,350,000 

91 

.  1218 

1.340 

4,118 

1,300,0(X) 

91 

.  1195 

1.315 

3,965 

1,2.')(),0(X) 

91 

.1172 

1.289 

3, 813 

1,200,(X)0 

61 

.1403 

1.263 

3,660 

1,1.50,000 

61 

.1373 

1.  236 

3,508 

1,100,000 

61 

.  1343 

1.209 

3,3.55 

1,0.50,00(J 

61 

.  1312 

1.181 

3,203 

i,m)o,i)oo 

61 

.1280 

1.152 

3,050 

9.50,  iKK) 

61 

.1247 

1.122 

2,898 

91H),  000 

61 

.  1214 

1.093 

2,745 

S.50,0(_)0 

61 

.1180 

1.062 

2,593 

800,000 

61 

.1145 

1.031 

2,440 

7.50,  (XK) 

61 

.  1108 

.997 

2,288 

700,  ax) 

61 

.1071 

.964 

2, 135 

6.50,  (KK) 

61 

.1032 

.929 

1,983 

600,000 

61 

.0991 

.892 

1,830 

5.50, 000 

61 

.0949 

.854 

1,678 

■500,  (KM) 

61 

.0905 

.815 

1,525 

4.50,  (HR) 

37 

.1103 

.772 

1,373 

4CW,000 

37 

.1039 

.727 

1,220 

3.50,000 

37 

.0972 

.680 

1,068 

300,  (HK) 

37 

.0900 

.630 

915 

2.50, 000 

37 

.0821 

.575 

763 

Wires. 

Size, 

Outside 

Weight 

B.  &  .S. 

Num- 
ber. 

Size. 

diameter. 

per 
1,000  feet. 

Inch. 

Inch. 

Pounds. 

0000 

19 

0. 1055 

0. 528 

645 

000 

19 

.0941 

.471 

513 

00 

19 

.0837 

.419 

406 

0 

19 

.0746 

.373 

322 

1 

19 

.0663 

.332 

2.55 

.0975 

.293 

203 

3 

.0866 

.260 

160 

4 

.0771 

.231 

127 

.') 

.0688 

.206 

101 

6 

.0612 

.184 

80 

8 

.0484 

.145 

50 

10 

.0386 

.116 

32 

12 

.0306 

.092 

20 

14 

.  0242 

.073 

12 

16 

.0193 

.058 

8 

18 

.0151 

.045 

5 

(415) 


36  Signal  Corps  Manual  No.  3. — Chapter  9. 

Carrying  capacity  of  insulated  copper  tvires  for  interior  wiring. 

NATIONAL  ELKCTRICAL  CODE. 


B.  &  S. 
Co 

Rubber- 

Weather- 

Rubber- 

Weather- 

Area. 

covered 

proof 

Area. 

covereil 

proof 

wires. 

wires. 

wires. 

wires. 

Cir.  viih. 

Amperes. 

Amperes. 

Cir.  mils. 

A  mperes. 

Amperes. 

IS 

1,624 

3 

5 

200,000 

200 

300 

16 

2,583 

6 

S 

300,000 

270 

400 

14 

4,107 

12 

16 

4(K),  0(K) 

330 

500 

12 

6,530 

17 

Zi 

.500,  WKl 

390 

590 

10 

10, 380 

24 

32 

60(),IK)0 

450 

680 

s 

16,510 

33 

46 

700,  IMK) 

.500 

760 

6 

26, 250 

46 

65 

8U0, 000 

550 

840 

0 

33, 1(X) 

54 

77 

900,  (KK) 

600 

920 

4 

'11,740 

65 

92 

1,(HK),IKK) 

650 

1,000 

3 

.52,6.30 

76 

110 

1,1IK),(K)0 

690 

1,080 

2 

66, 370 

90 

131 

1,2(K),(H)0 

730 

1,150 

1 

.S3,  690 

107 

156 

1,3(K),(X)0 

770 

1,220 

0 

105,  .500 

127 

185 

1,400,000 

810 

1,290 

00 

133,  1(X) 

150 

220 

1,,')00,0(X) 

850 

1,360 

0(W 

167,  800 

177 

262 

1,600,  (XX) 

890 

1,430 

0000 

211,600 

210 

312 

1,700,000 
1,800.000 

930 
970 

1,490 
1  550 

1,9(X),(X)0 

1,010 

1,610 

2,000,000 

1,050 

1,670 

' 

1 

Carrying  capacity  of  stranded  copper  conductors  for  interior  tviring. 
NATIONAL  ELECTRICAL  CODE. 


B.  &S. 
gauge. 

Area  actu- 
al C.  M. 

Number  of 
strands. 

Size  of 
strand,  B. 
&  S.  gauge. 

Amperes. 

19 
18 
17 
16 
15 
14 
12 

1,288 

1,624 

2,048 

2,583 

3,257 

4,107 

6,530 

9,016 

11,  .368 

14,336 

18,081 

22,799 

30, 856 

38, 912 

49,077 

60,088 

75, 776 

99,064 

124,928 

1,57,  .5(5.3 

198, 677 

2.50, 527 

29(5, 387 

373, 737 

413,639 

6 

12 

17 

21 

25 

30 

35 

40 

50 

60 

70 

85 

1(X) 

120 

145 

170 

200 

235 

270 

320 

340 

7 
7 
7 
7 
7 

19 
19 
19 
37 
37 
61 
61 
61 
61 
61 
91 
91 
127 

19 
18 
17 
16 
15 
18 
17 
16 
18 
17 
18 
17 
16 
15 
14 
15 
14 
.     15 

For  aluminuin  wire  the  carryiiifi  capacily  of  any  jiiven  size  is  to  bo  taken  as 
84  per  cent  of  the  value  given  in  tiie  above  table. 


(416) 


Miscellaneous  Tests  and  General  Information, — Chapter  9. 


us  SIGNAL  CORPS 


TABLES  OF  TEMPERATURE  COEFFICIENTS 

FOR  REDUCING  CONDUCTOR  AND  INSULATION  RESISTANCE! 
TO  STANDARD  TEMPERATURE 


Fig.  9-33.— TEMPERATURE  COEFFICIENTS. 
(417) 


38  Signal  Corps  Manual  No.  3. — Chapter  9. 

USEFUL   CONSTANTS  ANU  FORMULA. 

I  From  Electrical  Tables  and  FormuliP.  Clark  and  Sahinc.  ] 

coppEi:. 

The  specific  gravity  of  copper  wire,  according  to  tlie  best  autliorities,  is 
about  8.899. 

One  cubic  foot  weighs  about  550  pounds. 

One  cubic  incli  weighs  0.32  pound. 

The  ordinai-y  breaking  weigiit  of  copper  wire  is  about  17  tons  per  square 
inch,  varying  greatly,  however,  according  to  the  size  and  degree  of  hardness. 

The  weight  per  nautical  mile  of  any  copper  wire  is  about ..  pounds,  d  being  the 
diameter  in  mils. 

The  weight  per  nautical  mile  of  a  copper  strand  is  about  — -—  pounds. 

/0.4 

(P 
The  weight  per  statute  mile  of  any  copper  wire  is  —  pounds.     A  mile  of  64  mils 

diameter,  wire  weighs  in  practice  from  63  to  66  pounds. 

Tlie  diameter  of  any  copper  wire  weighing  lo  pounds  per  nautical  mile  is  7.4 
\/io  mils. 

Tlie  diameter  of  any  copper  wire  weighing  iv  pounds  per  statute  mile  is  7.94 
^/w  mils. 

The  diameter  of  a  copper  strand  weighing  w  pounds  per  nautical  mile  is 
about  8.4  y/w  mils. 

The  approximate  resistance  of  a  nautical  mile  of  pure  copper  weighing  1 
pound  is,  at  32°  F.,  1,091.22  ohms;  at  60°  F..  1,155.48  ohms;  at  75°  F.,  1,192.45 
ohms. 

The  resistance  per  nautical  mile  of  any  pure  copper  wire  or  strand  weighing  tt' 

poundsi8^^^'^at75°F. 

w 

The  resistance  per  nautical  mile  of  any  pure  copper  wire  d  mils  in  diameter 

is  ^^^?^  ohms  at  75  F. 
d^ 

The  resistance  per  statute  mile  of  any  pure  copper  wire  is  —-„-  ohms  at  60°  F. 

The  resistance  per  nautical  mile  of  any  pure  copper  strand  is  — -—  dims  at  75°  F. 

Tiio  resistance  per  nautical  mile  of  a  cable  conductor  is  equal  to  120,000 
divided  l)y  the  itroduct  of  the  [lercentage  conductivity  of  the  copper  and  its 
weight  per  nautical  mile  in  pounds. 

The  resistance  of  a  statute  nnle  of  pure  copper  weighing  1  ixmnd  is  1002.4 
ohms  at  00"  K.  51  mils  diiimeter  copper  wire  of  good  quality  has  a  resistance 
of  about   19  (iliiiis. 

The  rcHislaiici-  of  a  Htatntc  mile  of  pure  cojjpcr  weigliing  ■?/'  pounds  is — — olxms 

at  60°  V. 

Tho  resistance  of  any  pure  cojjijcr  wire  L  iii<'lu«  in  length,  weighing  n  grains,  is 

.001516  X  L"^     , 

olims. 
n 

(418) 


Miscellaneous  Tests  and  General  Information. — Chapter  9.  39 


The  weight  of  any  iron  wire  per  nautical  mile  is  — —  pounds,  f/ being  its  diameter  in 

mils. 
The  weight  of  any  iron  w-ire  per  statute  mile  is  -  -  pounds. 

The  diameter  of  ;iny  iron  wire  weiglung  ic  ])ouii(ls  per  stiitute  mile=8.49V'(r 
mils. 

'Die  tlianiett'r  of  any  iron  wirt'  weigiiini;'  ic  pounds  pel'  naulieai  iiiile=7.91  V'<c 
mils. 

Tiie  conductivity  of  ordinary  galvanized-ir()n  wire  averages  at)out  one-seventh 
that   of  pure  copper. 

The  resistance  per  statute  mile  of  a  galvanized-iron  wire  is  about  -  ^^ —  ohms, 
at  00°  F. 

C.\B1.K    TANKS. 

To  find  the  capacity  of  a  circular  tank : 

Let  r=radi\is  in  inches  of  eye. 

/v'^^radius  in  inches  of  the  tank. 
d= diameter  in  inciies  of  the  cable. 
/(=lieis;lit  in  inclies  of  tank. 
7r=3.1416. 

Total  length  of  cable  in  feet  -^  (R^-r^)  -f-  12. 

DISTANCE SOUND, 

Distance  from  shoi'e — Menfiurcment  by  sound. — It  sometimes  happens  that 
the  distance  of  the  ship  from  sliore  is  required  to  be  known,  and  a  measure- 
ment l)y  sound  may  be  resorted  to.  For  this  purpose  a  gun  is  hred  and  the 
interval  between  the  flash  and  the  sound  noted.- 

Let /)=distance  in  nautical  miles. 

T=temperature  of  air  in  degree  Centigrade; 
)S=interval  in  seconds ; 
then 


7)=0.179   SV1+().(X)374  T. 

Example:  A  ship  fired  a  cannon,  and  the  sound  was  heard  six  and  one-half 
seconds  after  the  flash  was  seen.  The  teniperature  of  the  air  was  1.""  C. 
Required,  tlic  distance   (/))   of  tlie  ship. 


/)  =0. 179 XGiV  1+0.00374X1") =1.2  nautical  miles. 

For  converting  statute  miles  to  nautical  miles,  nuiltiply  by  1.1528.  Nautical 
ndle  and  knot  are  .synonymous,  but  nautical  mile  is  used  to  express  distance  and 
knot    is  used  to  express  speed. 


(419) 


40  Signal  Corps  Manual  No.  3.— Chapter  9. 

List  of  Installed  Signal  Cokps  Submarine  Cables,  September  2.  1915. 

This  list  is  subject  to  change,  however  when  a  submarine  cable  is  replaced  a 
new   number  is  assigned. 

CABLES  IN  THE  UNITED  STATES. 


No. 


267 
311 
257 
345 
256 
306 
349 
266 
309 
264 
350 
260 
261 
346 
128 
265 


352 
348 
131 
332 
351 


135 
252 

138 
236 
237 
327 
220 
307 
231 
232 
274 
275 
2:J8 
239 
2.W 
328 
136 
320 
321 


277 
141 
279 
280 


298 
344 
299 
273 
3 13 
272 
312 
305 
220 
3.30 
Z51 
295 
329 
35;J 


T-ocation. 


Fort  Williams— Fort  Levett . . . 

....do 

House  Island— Fort  Levett 

...do 

House  Island— Fort  Preble 

....do 

....do 

Fort  McKinley — Long  Island. . 
Fort  McKinley — Peaks  Island. 

do 

...do 

Fort  Levett — Peaks  Island 

....do 

...do 

Fort  McKinley — Fort  Lyon . . . 
do 


NEW  HAMPSHIRE 


Fort  Constitution — New  Reservation. . 

Fort  Constitution — Fort  Stark 

Fort  Stark— Fort  Foster 

....do 

F.  C.  Station— Cable  Pole,  Fort  Foster. 


M.\SS.\CHUSETTS. 


Long  Island — Moon  Head 

Long  Island— Moon  Head  (North  Cable) . 

Fort  Andrews— Fort  Revere 

...do 

.  ...do 

Deer  Island— Fort  Standi-sh 

Fort  Heath— Nahant 

Fort  Heath— Deer  Island 

Fort  Standish— Fort  Warren • 

do 

Fort  Warren— Fort  Andrews 

....do 

Fort  Revere — Point  AUerton 

Point  Allerton— Strawberry  Hill 

Fort  Strong — Fort  Standish 

do 

Fort  Strong— Fort  Warren * 

Fort  Rodman— Richt'lson  Point 

do 


RHODE  ISL.VND. 


Fort  Adams— Fort  Wetherill 

Fort  Wetherill — Head  of  Mackerel  Cove. 

Fort  Greble — Fort  Kearney 

Fort  (Jetty — Fort  tireble 


NEW  YORK. 


Fort  Terry— Fort  Micliie 

Fort  Michie— Fort  H.  (i.  Wright 

Fortir.  ('..  Wright— iMirtMausfieid,  U.  I 

Fort  H.  <i.  Wriglu— .Vverys  Point,  Conn 

....do 

Fort  Slocuin— New  Rochelle  (Q.  M.  C.  cable) 

Fort  Slocura — New  Rochelle 

Fort  Tolton— Fort  Schuyler 

(loveruors  Island— Barge  oilice  (Q.  M.  ('.cable). 

Kort  Wood— Kills  Island 

Fori  Hunillton — Fort  Wadsworth 

do 

Fort  Wadsworth— Fort  Hancock,  N.J 

F.llis  Island— Barge  Ollico 


(420) 


Miscellaneous  Tests  and  General  Information. — Chapter  9.  41 

CABLES  IN  THE  UNITED  STATES— Continued. 


Location. 


Con- 
duct- 
ors. 


Date 
laid. 


DELAWARE. 


Fort  Du  Pont — Fort  Delaware. . 
Fort  Delaware— Fort  Mott,  N.J. 
do 


MARYL.\ND. 


Fort  Howard— Fort  Smalhvood . . . 

Fort  Carroll — Fort  Armislead 

Fort  \Va.shinglon— Fort  Hunt,  \'a. 
Fort  Howard— Fort  Carroll 


Fort  Monroe — Fort  Wool 

Around  McGinnis  I^and  (Fort  Monroe) . 


NORTH  CAROUNA. 


Fort  Caswell— Southport . 


SOUTH  CAROUNA. 


Fort  Moultrie — Fort  Sumpter . 
do 


Fort  Dade— Fort  De  Soto 

Fort  Dade — Shaws  Point 

Fort  De  Solo,  main  base  line . . 
Fort  Barrancas — Fort  Pickens. 

....do 

....do 

Fort  McRefr— Fort  Pickens 

....do 

....do 

Fort  McRee — Fort  Barrancas.. 
Fort  Taylor— Martello  Tower. . 


Fort  Morgan — Fort  Gaines 

Fort  St.  Philip — Fort  Jackson. .. 
Fort  Crockett— Fort  San  Jacinto. 


LOUISIANA. 


CALIFORNIA. 


Presidio — Fort  Baker 

Fort  Baker— Fort  McDowell. 
....do 


Alcalraz  Island — Angel  Island 

Fort  Barry— Fort  Miley 

Fort  Rosecrans— Fort  i'io  Pico 

Fort  Baker— Presidio  San  Francisco. 


WA.SHINGTON. 


....do... 

Fort  Flagler— Fort  Casey . . 

Fort  Casev — Fort  Worden . 


.do. 


44 

44 

6 

Fort  Lawton — Fort  Ward 1 

Fort  Lawton— Fort  Flagler 1 

Discovery  Bay— Between  station  (2)  and  end  of  aerial  line 22 

Discoverv  Bav— Between  stations  (2)  and  (3) 22 


Fort  Columbia— Fort  Stevens,  Oreg 44 

Fort  Columbia — Fort  Canby. 24 

Fort  Flagler— Fort  Worden. •' 10 

44 


(421) 


42 


Signal  Corps  Manual  No.  3. — Chapter  9. 

CABLES  IN  PANAMA. 


No. 


I-ocation. 


Date 
laid. 


371 
372 
373 
374 
375 
376 
377 
378 
379 
380 


PANAMA. 

Fort  Sherman — Fort  De  Lesseps 

Fort  De  Lesseps— Crist ol>al  Mole 

Fort  De  Lesseps — Fort  Randolph 

Galeta  Point — Largo  Remo  I'oint 

Fort  Aniatlor — Naos  Island,  Fort  Grant 

Xaos  Island,  Fort  Grant — Paitillo  Point 

Xaos  Island,  Fort  Grant— Batelle  Point , 

Naos  Island,  Fort  Grant — Perico  Island,  Fort  Grant 

Perico  Island,  Fort  Grant — Flamenco  Island,  Fort  Grant 
Flamenco  Island,  Fort  Grant— San  Jose  Rock , 


CABLES  IN  THE  PHILIPPINE  ISLANDS. 


343 
339 
340 
324 
356 


Malinta  Cove— Bavakaguin  Point 2  1913 

Fort  Mills— Cal.allo  Island 20  1913 

CabaUo  Island— El  Fraile  Island 20  i  1913 

Manila— Fort  Mills 1  1913 

Fort  Frank— Fort  Drum 50  1914 


CABLES  IN  ALASKA. 


Safety— St.  Michael  (abandoned;  partly  recovered  Aug.  15, 1905) 

Juneau — Skag:\vay  (changed  to  cables  Nos.  45  and  46) 

J  uneau — Haines  ' 

Haines— Skagway ' 

Sitka— Juneau  (via  Cape  Fanshaw) 

Seattle — Sitka 

Sitka — Valdez 

Valdez— Liscum 

Valdez — Seward  (changed  to  cables  Nos.  59  and  60) 

Fanshaw— Wrangell 

Wrangell— Hadle  y 

Hadley — Ketchikan 

Sitka— Japonski  Island 

Seward— Montague  Island  -' 

\'aldez — Montague  Island  - 

Cordova— Montague  Island 

Juneau — Douglas  City 

Cordova — Cape  Whiteshed 


1901 
1901 
1903 
1903 
1903 
1901 
1904 
1905 
1905 
1906 
190(> 
1906 
1907 
1908 
1908 
1908 
1910 
1908 


»  Formed  by  dividing  the  Juneau-Skagway  cable,  No.  44,  at  Fort  William  H.  Seward  and  replacing 
portions  near  Skagway. 
■■!  Formed  by  dividing  the  Valdez-Seward  cable,  No.  51,  at  Montague  Island. 


(422) 


Chapter  10. 
requisitions  and  general-maintenance  regulations. 

KKQUISITION.S    FOK   MAINTENANCK   SUPPLIES. 

Except  in  emergency,  all  property  shipped  Iroin  any  of  tlio  Sijxnal  Corps 
general  supply  depots,  except  the  one  at  Manila,  1'.  I.,  and  liic  one  at  Seattle, 
Wash.,  is  directed  shipped  by  the  Chief  Signal  Ofhcer  of  the  Army.  The  amount 
of  stock  on  hand  at  each  of  the  supply  depots  is  continually  and  directly  under 
the  observation  of  one  oflice.  This  results  in  efficiency  and  economy  in  the 
purchase  and  issue  of  property.  With  one  office  handling  all  requisitions  for 
fire-control  and  Signal  Service  property  from  all  Army  posts  in  continental 
United  States,  Hawaii,  Porto  Rico,  United  States  territory  in  Cuba,  and  the 
Canal  Zone,  together  with  all  requisitions  from  the  various  State  militia  organi- 
zations and  the  voluminous  stock  requisitions  from  the  various  property  officers 
of  the  different  supply  depots,  it  is  not  difficult  to  .see  that  the  efficient  and 
expeditious  handling  of  papers  and  subsequent  furnishing  of  supplies  devolves 
in  a  great  measure  upon  those  authorized  to  submit  requisitions. 

An  effort  should  be  made  to  submit  these  requisitions  semiannually  only. 
However,  it  is  not  intended  that  any  restriction  whatever  be  placed  regarding 
the  number  of  requisitions  to  be  submitted.  First  consideration  should  be  given 
to  having  necessary  supplies  on  hand. 

A  little  care  exercised  by  those  who  prepare  requisitions  is  the  greatest  means 
of  assisting  those  concerned  in  supplying  the  desired  articles.  The  great  multi- 
plicity of  Signal  Corps  apparatus  throughout  the  United  States  and  its  posses- 
sions, which  of  necessity  was  invariably  purchased  from  the  lowest  bidder,  has 
been  manufactured  by  various  companies  and  individuals,  some  of  whom  are 
still  in  business,  while  others  have  ceased  to  manufacture. 

Hereafter  post  requisitions  for  Signal  Corps  supplies  will  be  serially  num- 
bered by  means  of  pen  and  red  ink.  The  number  should  be  aflixed  in  the  upper 
left-hand  corner  of  the  front  sheet  and  should  start  with  No.  1  at  the  beginning 
of  each  fiscal  year. 

All  post  requisitions  for  Signal  Corps  supplies,  except  those  from  militia 
organizations  and  pi-operty  officers  of  Signal  Corps  supply  depots,  should  be 
forwarded  to  the  Department  Signal  Officer  of  the  department  in  which  the  fort 
for  which  the  supplies  are  desired  is  located.  The  Department  Signal  Officer 
will  have  the  requisitions  examined,  make  such  revisions  as  in  his  opinion 
should  be  made,  check  the  .serial  numbers,  and  be  sure  that  all  provisions 
relating  to  requisitions  contained  in  this  manual  have  been  complied  with  before 
forwarding  them  to  the  Chief  Signal  Officer  of  the  Army. 

All  requisitions  from  the  various  State  militia  organizations  will  be  serially 
numbered,  starting  with  No.  1  at  the  beginning  of  each  fiscal  year.  These 
requisitions  will  be  forwarded  as  directed  to  the  Chief.  Division  of  Militia 
Affairs,  War  Department.  Washington,  D.  C.  who  will  carry  out  the  provisions 
relative  to  examination  contained  in  the  preceding  paragraph. 

All  requisitions  from  property  officers  of  Signal  Corps  supply  depots  should 
be  forwarded  direct  to  the  Chief  Signal  Officer  of  the  Army  when  such  requisi- 
tions are  in  accordance  with  all  regulations  contained  herein. 

(423)  1 


2  Signal  Corps  Manual  No.  3. — Chapter  10. 

All  requisitions  from  Signal  Corps  tield  companies  should  be  forwarded  to 
Department  Signal  Officer,  under  whose  control  the  company  is  operating  unless 
by  special  assignment  the  company  is  controlled  by  another  official,  in  the  event 
of  which  the  requisition  should  be  forwarded  to  such  official  who  will  see  that 
the  provisions  of  this  manual  have  been  complied  with,  and  then  forward  the 
requisition  to  the  Chief  Signal  Officer  of  the  Army.  Field  company  requisitions 
forwarded  to  department  signal  officers  shall  be  acted  upon  by  that  officer  in 
a  manner  similar  to  that  prescribed  above  for  post  requisitions. 

The  following  instructions  relative  to  items  of  property  appearing  in  requisi- 
tions should  be  observed : 

(«)  To  aid  in  furnishing  repair  parts,  a  number  of  tigures  illustrating  appara- 
tus in  this  manual  are  followed  by  a  list  of  parts  of  the  apparatus  shown  in  the 
figure,  and  in  most  instances  the  part  may  be  found  in  the  figure  by  means  of 
a  reference  number  placed  opposite  name  of  the  part.  In  rendering  requisitions, 
where  a  part  is  desired,  the  name  of  the  part  exactly  as  it  appears  in  the  list, 
followed  by  the  letters  "  P.  N.,"  should  be  given,  immediately  succeeded  by  the 
part  number  in  the  list  relating  to  that  particular  figure ;  also  figure  number 
should  be  entered.  In  addition,  the  numeral  "3"  in  parenthesis  should  appear  at 
end  of  item  in  order  to  distinguish  between  figures  similarly  numbered  in  Signal 
Corps  Manual  No.  S.  It  is  unnnecessary  to  name  the  apparatus  unless  some 
doubt  exists  as  to  whether  the  part  shown  in  the  list  is  what  is  wanted  or  if 
the  part  desired  is  not  listed.  AMiere  such  a  condition  exists,  a  full  descrip- 
tion of  the  part  should  be  furnished. 

It  is  important  to  note  that  in  listing  parts  of  some  of  the  apparatus  it  is 
absolutely  necessary  that,  in  addition  to  the  above,  either  the  manufacturer,  or 
the  size,  or  both  be  entered.  As,  for  instance :  A  set  of  elements  for  a  storage 
battery  could  not  be  intelligently  furnished  unless  the  size  and  the  manufac- 
turer's name  are  known.  This  also  applies  to  the  jars  and  sand  trays  for 
storage  batteries.  Bolt  connectors  and  electrolyte  for  telephone  storage  bat- 
teries can  be  furnished  without  knowing  either  the  size  of  the  battery  or  the 
name  of  the  manufacturer. 

Example : 

8  mica  insulators  for  choke  coil,  P.  N.  7,  fig.  6-1  (3). 

4  screws,  binding,  with  nuts,  P.  N.  8,  fig.  6-1  (3). 
6  nuts  and  washers  for  P.  N.  7,  fig.  6-2  (3). 

1  scale,  P.  N.  36,  fig.  4-30  (3). 

(ft)  In  listing  wood  screws,  type  of  head,  metal  employed,  length,  and 
gauge  size  should  be  entered  in  the  order  named  after  the  word  "  screws."  The 
word  "  bright  "  should  not  be  used  to  indicate  plain  iron.    Example : 

li  screws,  H.  H.  i)rass,  lA",  No.  30,  gross.     (R.  H.  means  round  head.) 
'.i  screws,  F.  H.  iron,  1",  No.  8.  gross.     (F.  H.  means  flat  head.) 
{(■)   In  listing  machine  screws  the  word  "machine"  should  follow  the  word 
".screws"  and  the  type  of  head.  iii('t;il  employed,  length,  gauge  size,  and  num- 
ber of  threads  per  iiicii  should  follow  in  the  order  named. 
Example: 

2  screws,  niiicliine,  F.   II.  iron,  lA",  8-32,  gross. 
6  screws,  nuidiine,  H.  H.  brass,  1",  10-24,  gross. 

5  screws,  machine.  Fillister,  Hd.  iron,  1",  12-24,  gross. 

Whore  screws  having  a  si)eciMl  finish  such  as  dull  nickel  are  desired  the  name 
of  finish  should  follow  the  name  of  metal  and  wiiere  dimensions  (other  than 
number  of  Ihrejids  per  inch)  are  not  of  connnercial  standard  a  sketch  illus- 
trating such  dimensions  should  accompimy  the  requisition. 

(424) 


Requisitions  and  General-Maintenance  Regulations. — Chapter  10.  3 

(d)  Tho  (liinonsions  iuid  inatorial  of  hrushos  for  motors  and  generators 
should  be  furnished,  and  if  flexible  wire  lead  forms  a  part  of  the  brush  desired, 
the  word  "  brushes  "  in  the  item  should  be  followed  by  the  iihrase  •'  with  pit: 
tails."  The  name  of  the  manufacturer  of  the  apparatus  with  which  the  brush 
is  to  be  used  should  be  given,  also  the  size  and  niaimfacturer's  serial  number 
of  tlie  apparatus  with  which  the  brush  is  to  be  used. 

Example: 

4  brushes  (one  set),  carbon,  i\"  x  1"  x  2",  for  motor  end  of  B.  C,  \  kw., 

motor  generator  No.  3421. 
2  brushes,  with  pig  tail    (one  set),  carbon,  \"  xl"  xli",  for  generator 
end  of  N,  G.,  i  kw.,  motor  generator  No.  6415. 
(r)   A  full   description  of  all  wire  furnished  by  the  Signal  Corps,  together 
with  proper  designation  of  each  of  the  various  types  will  be  found  in  Chapter 
VIII  of  this  Manual. 
Example: 

2  wire,  buzzer,  miles. 
3(W  wire,  fixture,  40  mils.  feet. 
200  wire,  weather-proof,  128  mils.  feet. 
(/)    In  listing  fuses,  the  Signal  Corps  type  number  and   the  ampere  rating 
should  be  given.    The  Signal  Corps  type  mnnber  may  be  determined  by  referring 
to  Chapter  VIII  of  this  Manual.     If  fuses  desired  do  not  cin-respond  with  any 
of  the  Signal  Corps  types,  the  name  of  manufacturer  of  apparatus  with  which 
it  is  to  be  used,  the  ampere  rating  desired,  and  if  practicable,  a  sample  shf)uld 
be  furnished. 
Example: 

10  fus(>s.  type  3.  20  ampere. 
20  fuses,  type  9.  1  ampere. 

50  fuses.  1  ampere,  for  C  W.  conimon  baity,  telephone  switchboard,  sam- 
ple attached. 
20  fuses,  5  amp.,  for  Coke  5-S  can  terminal. 
(p)    In  entering  items  of  screw  anchors,  the  gauge  size  of  the  screw  to  be  used 
with  the  anchor  and  the  length  of  anchors  desired  should  be  shown. 
Example: 

100  screw  anchors  for  No.  10  screws,  1". 
(/()   Either  a  sketch  or  principal  dimensions  of  toggles  requisitioned  should 
be  submitted. 
Example: 

50  toggles,  bolt,=i"  X  approx.  3";  cross  piece  24"  long. 
(0  Items  of  switches  should  show  type  (knife  or  snap)  and  ampere  rating. 
Items  of  snap  switches  should  also  show  whether  double  pole,  single  pole,  or 
three  way.  Items  of  knife  switches  should  also  show  whether  double  pole, 
single  pole,  or  triple  pole,  and  whether  double  or  single  throw.  If  fused 
switches  ai'e  desired  it  should  be  so  stated. 
Example: 

2  switches,  snap,  10  ampere,  D.  V. 
1  switch,  knife,  15  ampere,  S.  P.  D.  T. 
When    knife    switches,    without    bases,    for    mounting    on    switchboards,    are 
desired,  reference  should   be   made   to  either   Signal  Corps   drawing  381   E-1 
or  Signal  Corps  drawing  382  E-1. 


(425) 


4  Signal  Corps  Manual  No.  3. — Chapter  10. 

ij)  Where  heat  coils  are  listed,  the  name  of  the  manufacturer  or  a  sample 
should  be  furnished. 

Example: 

50  heat  coils,  W.  R.  Growler. 
100  heat  coils,  sample  attached. 

(/.•)  The  great  variety  of  cords  used  with  apparatus  supplied  by  the  Sipiial 
Corps  makes  furnishing  of  satisfactory  renewals  an  extremely  difficult  one. 
An  effort  has  recently  been  made  to  standardize  all  cords  and  cord  terminals, 
and  it  is  believed  that  those  entering  renewals  on  requisitions  will  find  the  Sig- 
nal Corps  number  of  cord  desired  by  referring  to  chapter  8.  It  is  intended  that 
in  the  future  purchase  of  apparatus  utilizing  cords,  that  manufacturers  will 
be  required  to  select  cords  to  be  furnished  from  drawings  in  accordance  with 
(••ird  illustrations  shown  in  chapter  8.  If  possilile,  cords  should  be  designated 
by  mmiber  only.     If  this  is  impossible  a  sample  should  bo  submitted. 

Example: 

6  cords,  No.  4. 
4  cords,  No.  5. 

8  cords  for  obsolete  distributing  switchboard,  as  per  sample  inclosed. 
(/)  In  submitting  requisition  for  cable  to  be  used  in  extension  of  systems 
it  is  desirable  to  have  the  necessary  lengths  entered,  as  a  record  of  short 
lengths  of  serviceable  cable  is  kept  in  the  office  of  the  Chief  Signal  Officer  of 
the  Array  and  such  information  results  In  the  issue  of  lengths  that  otherwise 
take  up  valuable  room  at  supply  depots.  If  the  cable  is  to  be  trenched  it 
should  be  so  stated. 
Example: 

800  feet  cable,  type  213,  lengths  350-220-230. 
325  feet  cable,  type  401,  length  325. 
1,200  feet  cable,  type  217,  trenched. 

CAKK    OF    POST    TELEPHONE    AND    SMALL    ARMS    TARGET    RANGE    SIGNALING     SYSTEMS. 

General  Orders  No.  90,  1910,  which  pertain  lo  the  maintenance  of  post 
telephone  and  small  arms  target  range  signaling  systems,  is  entered  below 
for  the  guidance  of  all  concerned. 

Tiie  following  instructions  for  the  operation,  maintenance,  and  care  of  post- 
telephone  systems  and  the  buzzer  and  connnunication  systems  of  target  ranges 
installed  by  the  Signal  Corps  are  publish(>d  : 

1.  The  route  and  location  of  duct  lin(>s  and  troncluMl  cabk>s  on  posts  and 
fither  military  reservations  will  be  carefully  recorded,  and  copies  of  these 
records  furnished  to  the  respective  post  quartermasters.  Officers  in  charge 
of  construction  will  in  all  cases  see  llinl  no  excavating  or  trenching  is  <lone 
on  any  post,  or  oth(>r  military  reservation,  without  jinniously  ascertaining 
the  location  of  the  cables  and  ducts  installed  thereat  and  determining  that 
these  will  not  be  injured  by  the  contemplated  work. 

2.  It  will  be  the  duty  of  the  officer  resi)onsible  Cor  Signal  Corps  property 
to  see  that  the  cables  are  projierly  trenched  and  that  the  manholes  and  outlets 
sire  at  all  times  properly  covered  with  soil  to  the  extent  intended.  Heavy 
rains  or  other  cau.ses  nuiy  expo.se  any  of  these,  and  thereby  subject  them  to 
damage.  The  outlet  case  pipes  will  be  kept  in  their  original  position  by 
maintaining  ilic  soil  about  them  in  m  tirni  coinlit  ion.  'Die  manholes  are  to  be 
c-oVered  with  (5  inches  of  soil,  and  no  cable  or  conduit  is  intended  to  be  nearer 
tlutn  18  inches  to  the  surface.     If  any  cables  are  injured  by  exposure,  immedi- 

(426) 


Requisitions  and  General-Maintenance  Regulations. — Chapter  10.  5 

ate  steps  will  be  taken  to  repair  them,  (tr  if  it  is  Impossible  to  do  this,  tempo- 
rary steps  will  be  taken  to  i)revent  further  injury,  ami  report  made  through 
proper  chaiuiels  to  the  Department  Signal   Olliccr. 

3.  The  greatest  care  will  be  exercised  in  handling  lead-covered  cables,  as 
tlie  paper  which  forms  the  insulation  of  the  core  takes  up  moisture  very  readily, 
in  which  event  the  cable  rapidly  becomes  unserviceable. 

4.  Underground  conduit  systems  at  posts  will  be  connected  when  practicable 
to  the  post  drainage  system,  and  underground  conduit  systems  on  target  ranges 
will  also  be  provided  with  adeipiate  drainage.  It  is  necessary  to  keep  surface 
water  from  draining  into  outlet  case  pipes,  as  the  outlet  itself  is  not  intended 
to  withstand  constant  submerging. 

5.  To  insure  that  the  target  range  equipment  is  complete  and  in  a  condition 
to  give  satisfactory  service  for  the  target  season,  the  officer  re.sponsible  for 
this  equipment  will  see  that  the  material  is  reinstalled  and  connected  and  a 
thorough  test  made  of  all  the  equipment  one  month  or  more  before  the  com- 
mencement of  the  target-practice  season.  If  any  material  proves  defective  an 
iiinnediate  report  will  be  made  fo  the  Department  Signal  Odicer,  in  which  the 
nature  of  any  defect  will  be  fully  stated,  so  that  the  material  and  labor  neces- 
sary for  its  correction  may  be  provided  before  the  opening  of  the  practice 
season. 

6.  At  the  end  of  the  practice  season  all  buzzers,  strap  keys,  annunciators, 
master  switches,  and  telephones  which  might  be  stolen  or  become  damaged  by 
exposure  will  be  removed  from  their  points  of  installation  to  the  storehouse. 

7.  Doors  of  cable  or  distributing  boxes  placed  outside  of  buildings  or  on  poles 
will  be  kept  closed  at  all  times  when  not  in  use. 

8.  All  aerial  cables  will  be  jirotected  by  fuses  so  that  lightning  or  other 
foreign  electrical  currents  may  not  enter  the  cable  under  any  circumstances. 
Particular  care  will  be  taken  that  these  fuses  are  in  serviceable  condition  at 
all  times. 

INSPECTION     OF     POST     TELEPHONE     AND     SMALL     AKMS     TARGET     KANGE     SIGNALING 

SYSTEMS. 

An  extract  of  G.  ().  5,  W.  D.,  1913,  follows : 

The  systems  at  interior  posts  will  be  inspected  twice  annually  by  a  competent 
inspector  having  technical  knowledge  of  nuigneto  and  conunon  battery  systems, 
these  inspections  to  be  made,  if  practicable,  during  the  two  months  prior  to 
July  1  and  .January  1  of  each  year. 

The  report  covering  these  inspections  will  be  prepared  in  triplicate  on  Signal 
Corps  forms  Nos.  L'Ul)  and  211.  one  copy  to  be  retained  for  the  files  of  the 
signal  officer  of  the  post,  and  the  other  two  forwarded,  through  military 
channels,  for  the  files  of  the  department  signal  officer  of  the  Territorial  division 
concerned  and  tlie  Chief  Signal  Officer  of  the  Army. 

Department  signal  officers  of  the  Territorial  divisions  will  apply  for  the 
necessary  orders  to  have  the  above-mentioned  inspections  made. 

MAINTENANCE    TEST. 

In  the  maintenance  of  any  electrical  system,  especially  where  underground 
or  aerial  cable  is  involved,  it  is  advisable  to  occasionally  ascertain  the  insula- 
tion resistance  of  the  circuits. 

With  the  important  fire-control  .systems  at  our  seacoast  defenses,  it  is  re- 
quired that  this  action  be  taken  once  a  month,  and,  although  it  is  not  required 
for  post-telephone  and  small-arms  tai-get-range  systems  at  interior  posts,  it  is 
.advisable  to     make  an  occasional  test  incident  to  the  general  maintenance  of 

46581°— 17 28  (427) 


6  Signal  Corps  Manual  No.  3. — Chapter  10. 

the  systems.  By  this  means  a  partial  fault,  which  in  time  might  result  in 
several  circuits  becominc;  inoperative,  may  be  detected. 

There  are  several  methods  of  making  the  test,  the  quickest  and  simplest  being 
with  an  instrument  termed  "  megger."  The  Signal  Corps  has  a  limited  number 
of  these  instruments,  and,  although  they  are  not  regularly  issued  for  the 
purpose,  department  signal  ofiicers  usually  have  one  that  can  be  furnished 
temporarily. 

Prior  to  making  this  test,  the  lines  should  be  tested  by  operating  the  appara- 
tus connected  thereto,  and  any  defects,  however  trilling,  should  l)e  noted. 

Tlie  megger. — The  megger  shown  in  figure  10-1  is  a  direct  reading  instru- 
ment, the  type  usually  furnished  having  a  scale  0-.5  megohms. 

Current  for  its  operation  is  obtained  by  means  of  a  hand-driven  generator 
forming  a  part  of  the  instrument.  In  revolving  the  armature  the  revolutions 
per  minute  should  be  increased  until  the  crank  tends  to  slip.  The  slipping 
effect  is  caused  by  a  mechanical  governor  which  is  intended  to  maintain  a 
constant  speed. 


I 

Fn 

M 

xJ4 

^     '■ 

CIRCUITS 


Fig.    10-1.— MEGGER. 

The  lest  consists  of  measuring,  to  limit  fixed  by  instrument  used,  the  ins»i- 
hiiioM  between  each  conductor  of  tin;  system  and  ground.  It  is  not  intended 
liiat  the  iiiu^s  shall  be  disconnected  either  at  instruments  or  at  cable  terminals. 
An  exception  to  this  is  made  in  testing  lines  of  a  post-telephone  system.  These; 
line.s  are  ordinarily  tested  at  the  lightning-arrester  strip,  where,  by  insertion  of 
a  .special  plug,  circuit  to  teleplione  switchboard  is  disconnected  and  outgoing 
line  is  coiin<?cted  to  ground  tlirougli  the  testing  instrument. 

('are  should  be  taken  not  to  be  mish>d  into  believing  lini;  wire  or  cable  is 
defective  when  low  insulation  is  due  to  leakage  between  carbons  of  lightning 

(428) 


Requisitions  and  General-Maintenance  Regulations. — Chapter  10.  7 

arresters.  When  power  lines  are  tested,  switches  l),v  which  the  circuits  are 
controlled  should  be  openeil. 

In  niakinj^  the  tests  with  me}:;rer  attacii  a  wire  to  binding  post  of  megger 
marked  "ground,"  connecting  other  end  of  wire  securely  to  sheath  of  cable 
being  tested.  Attach  a  well-insulated  wire  to  the  remaining  binding  post  of 
the  megger  for  connection  to  lines  to  be  tested,  and  be  sure  that  the  instrument 
is  well  insulated  from  earth. 

Revolve  generator  crank  handle,  increasing  speed  of  rotation  until  crank 
tends  to  slip,  and  with  test  wire  make  contact  with  lines  to  be  tested.  With 
lines  in  good  condition,  rapid  progress,  can  be  made,  as  it  is  only  necessai-y  to 
touch  forcibly  each  line,  going  from  one  to  another  in  rapid  succession. 

The  maintenance  test  can  be  made  with  a  voltmeter.  Sufficient  number  of 
dry  cells  should  be  used  to  obtain  nearly  maximum  scale  reading.  A  .special 
voltmeter  having  a  100,000  ohm  coil  was  originally  furnished  for  making  main- 
tenance tests.  This  voltmeter  is  termed  "  post  testing  voltmeter  "  and  is  shown 
in  figure  10-2.     It  will  be  noted  that  specific  value  of  Insulation  can  not  be 


I 


Fig.  10-2— VOLTMETER,  POST  TESTING. 


obtained  unless  resistance  of  voltmeter  coil  is  known  and  that  the  higher  the 
resistance  of  this  coil,  the  higher  the  value  of  insulation  that  can  be  measured. 
If  a  voltmeter  is  used  in  making  maintenance  test,  proceed  as  follows: 
(1  )   Try  the  line,  for  actual  operation,  and  note  any  and  all  defects,  however 
trifling. 

(2)  Connect  the  +  terminal  from  the  battery  to  the  ground,  utilizing  the 
sheaths  of  cable  being  testetl. 

Be  sure  that  you  have  a  good  ground. 

(3)  Connect  the  other  outside  terminal  of  the  battery  to  one  side  of  the 
voltmeter. 

(4)  Connect  a  well-insulated  testing  lead  to  the  remaining  terminal  of  the 
voltmeter,  and  see  that  both  the  voltmeter  and  Ilic  liattery  are  w(>l!  insulated 
from  the  ground. 

(5)  Apply  the  free  end  of  the  testing  lead  to  the  grounded  end  of  the  battery 
and  note  the  reading,  which  will  be  called  V  and  should  cover  n(virly  the  whole 
scale  of  the  voltmeter. 

(6)  Remove  the  testing  lead  referred  to  in  .">  from  the  grounded  battery 
terminal  and  apply  successively  to  the  terminals  of  the  line  which  is  to  be 
tested,  the  reading  being  noted.     These  readings  are  called  V,. 

(7)  The  actual  insulation  resistance  of  this  circuit  may  be  determined  by  the 
formula ; 

•T'l) 


V. 

(429) 


8  Signal  Corps  Manual  No.  3. — Chapter  10. 

Rx  is  the  insulation  resistance,  and  lig  is  tlie  resistance  of  tlie  voltmeter  coil 
and  circuit,  which  will  be  found  inside  the  lid  of  the  case  and  which  varies 
slightly  with  individual  instruments. 

Should  any  of  the  short  lines  employed  show  an  insulation  to  ground  of  less 
than  1  megohm,  steps  should  be  taken  to  ascertain  the  cause  of  such  condition. 

The  maintenance  test  may  be  applied  at  any  point  in  a  circuit. 

Moist  atmosphere  will  cause  low  reading  of  the  megger  and  high  reading  of 
a  post-testing  voltmeter,  due  to  increased  surface  leakage,  and  tests  will  ordi- 
narily be  made  when  the  atmosphere  is  comparatively  free  of  moisture. 

If  it  is  thought  that  serious  leakage  occurs  when  atmosphere  is  comparatively 
moist,  the  difficulty  should  be  remedied  and  special  tests  should  be  made  during 
the  damp  period  to  determine  this  question. 

If  condition  cited  in  preceding  paragraph  is  found  to  exist,  disconnection 
of  instruments  or  terminal  boxes  will  usually  locate  the  leak ;  but  it  is  neces- 
sary that  any  leakage  which  may  develop  be  corrected  whether  it  be  in  cable, 
outlet  boxes,  switchboard,  or  in  the  instruments. 

Leakage  in  the  conductors  of  cables  is  obviously  more  serious  than  any 
other  form  of  fault  and  great  care  should  be  taken  in  order  to  be  sure  whether 
faulty  conductors  exist  by  eliminating  every  other  source  of  trouble  before 
reporting  the  cable  defective.  It  will  frequently  be  found  that  faulty  insula- 
tion develops  gradually,  and  that  readings  from  month  to  month  will  change 
in  such  a  way  as  to  make  it  possible  to  forecast  the  working  life  of  a  con- 
ductor. Arrangements  should  be  made  for  the  correction  of  such  a  condition 
as  soon  as  practicable  after  it  is  positively  known  to  exist. 

If  the  foregoing  instructions  are  faithfully  followed  no  absolute  interrup- 
tions of  important  lines  of  communication  should  occur  except  from  unusual 
accidents,  due  to  inadvertence. 

MAINTENANCE   INSPECTION. 

At  least  once  a  year  a  maintenance  inspection  should  be  made  of  all  appa- 
ratus of  post  telephone  and  small  arms  signaling  systems,  by  person  or  persons 
designated  by  local  post  signal  officer. 

This  inspection,  consists  of  an  examination  of  all  ai)])aratus  of  (he  systems. 

Contacts  should  be  examined  and  made  positive,  defective  telephone  nioutli- 
pieces  replaced,  and  inefficient  instrument  circuits  repairetl  before  trouble 
actually  occurs. 

All  external  connections  to  appai*atus  sliould  be  examined  for  possible  cor- 
rosion. A  strip  of  j)aper  should  l)e  drawn  between  platinum  contacts  for  the 
]»urpose  of  cleaning  them  and  to  make  sure  the  contact  is  properly  made. 
Only  hard-surfaced  pajjcr  should  be  used,  otherwise  paper  lint  may  collect 
and  cause  jioor  or  open  contact. 

( (rdiiiarily,  telcplione-traiisiiiitlcr  shells  should  not  be  oiieiied.  If  trouhU' 
arises  due  |o  defeciive  butloiis  the  Irniismitter  so  alfecled  shoidd  be  "tui'iied 
ill"  to  a  Signal  Corps  snpjily  depot  for  i-ei)air  and  return  aUvv  having  re- 
ceived |>io|per  antliorily  for  such  action.  Thos(>  making  this  inspection  sliould 
be  provided  with  an  inspector's  pock«>t  kit.  described  in  chapter  S;  a  telephone 
receiver;  a  jiiece  of  ehainois  skin;  a  jutrtable  voltmeter,  or  portable  voltam- 
nieter ;  atid  a  couple  of  tiexible  testing  cords  to  wiiicli  standard  si»ring  clips 
have  f>een  attached.  ( >ne  or  two  dry  cells  of  battery  will  t'recpieiilly  be  foiuid 
a   c(tnv<'nient   adjuiK-t    lor  use  in  testing  for  identification. 

The  inspection  described  above  is  a  matter  of  conmiercial  routine  which  is 
I»racticed  by  all  commercial  eoiii]»anies  alteniiiling  to  give  .satisfactory  service 

(430; 


Requisitions  and  General-Maintenance  Regulations. — Chapter  10.  9 

and   is  al)S()liit('ly  lu'ccssiiry   for  tlu'  prevention  of  tlie  various  serious  evils  to 
which  tile  hesi  of  electrical   installations  are  liable. 

MONTHLY     STORAGE-BATTEUY    REPORT. 

This  report  is  forwarded  to  the  Department  Signal  otficer  at  the  end  of  each 
month  by  the  post  signal  otlicer. 

The  report  consists  of  one  copy  of  Signal  Corps  form  260  dtily  acconiplislied 
for  each  Signal  Corps  storage  battery  attached  to  the  post.  Full  instructions 
relative  to  readings  to  be  taken  and  recorded  are  printed  on  back  of  the  form. 

MAINTEN.XNCE    OF    MOTOR    GENERATORS. 

The  motor  generator  should  be  kept  covered  when  not  in  use.  Care  in  this 
particular  will  save  the  machine  from  damage  by  du.st.  The  pneumatic  duster, 
which  is  supplied  to  keep  the  windings  clear  of  copper  particles  which  may  be 
thrown  off  by  the  commutators,  should  be  frequently  used.  Inspect  the  machine 
each  time  before  .starting,  to  make  sure  that  it  is  clean. 

Bcarhif/.s. — The  bearings  should  be  filled  with  tlie  highest  grade  of  dynamo 
oil  to  such  a  height  that  the  surface  of  the  oil  comes  above  the  lowest  point  of 
the  oil  rings.  If  the  bearings  are  too  full,  oil  will  be  throun  out  along  the  shaft 
and  get  into  the  armature  windings  and  commutator,  eventually  causing  trouble. 
The  oil  shotild  be  renewed  semiannually,  and  in  all  cases  should  be  filtered 
before  using  again.     It  is  preferred  that  oil  should  not  be  used  more  than  once. 

Keep  dry  and  clean. — Keep  the  machine  dry  and  clean.  An  accumulation  of 
dust  or  the  dripping  of  water  on  any  part  of  it  should  not  be  i>ermitted,  as  it 
will  cause  serious  trouble  in  a  very  short  time.  The  carbon  dust  from  the 
brushes  should  not  be  allowed  to  accumulate  on  the  brush  holders,  commutator, 
or  other  parts. 

By  means  of  a  bellows  or  air  blast  the  set  should  be  thoroughly  and  frequently 
blown  out,  inspection  being  made  each  time  to  determine  that  all  the  dust  and 
dirt  has  been  removed.  Satisfactory  results  can  not  be  expected  if  it  is  not 
properly  cared  for  and  given  attention  at  frequent  intervals.  The  life  of  any 
machine  is  increased  in  direct  proportion  to  the  attention  it  receives. 

Starting. — Before  starting  the  motor  generator  set  see  that  all  oil  wells  have 
a  proper  amount  of  oil  and  that  the  brushes  are  properly  adjusted.  With  motor 
generator  set  having  a  direct-current  motor,  see  that  the  handle  of  the  auto- 
matic starting  box  is  in  the  "stop"  position  before  closing  the  motor  main 
switch. 

After  being  sure  that  everything  is  in  readiness-,  close  the  motor  main  switch 
and  start  the  machine  slowly  by  moving  the  handle  of  the  automatic  starting 
box  step  by  step  toward  the  "  start "  position.  Be  sure  that  all  oil  rings  revolve 
freely.  The  lever  of  the  motor  starting  box  should  never  be  stopped  for  any 
length  of  time  until  the  last  step  has  been  reached.  When  this  step  has  been 
reached  the  magnetic  holder,  the  windings  of  which  are  in  the  field  circuit, 
should  hold  the  lever  at  the  last  stop.  If  for  any  reason  the  magnetic  holder 
fails  to  hold  the  lever,  or  shoidd  it  l)e  desired  to  stop  the  set  before  the  last 
.step  has  been  reached,  the  motor  main  switch  should  be  opened  befoiv  tdlowing 
the  starting-box  lever  to  i-eturn  to  the  "  stop  "  position. 

Regulate  the  voltage  of  generator  bj;  means  of  the  generator  field  rheostat. 

.\fter  imtting  the  generator  in  circuit,  feel  all  the  connections  of  both  machines; 
if  any  one  is  warmer  than  the  other  the  connection  is  imperfect  ami  should  be 
cleaned  ami  tightened. 

(4.S]) 


10  Signal  Corps  Manual  No.  3. — Chapter  10. 

Cnro  slioukl  be  taken  that  the  field  cireuit  t»L  a  motor  is  not  oiK^ned.  as  there 
is  (laiitrer  of  the  field  coils  iieinu'  punctured.  If  it  becomes  necessary  to  break 
the  lield  circuit,  it  sh(»uld  be  accomplished  slowly,  allowing  the  arc  to  die  out 
trradually. 

Stopping  o  motor-generator  set  having  a  direct-current  motor. — The  follow- 
ing points  should  be  observed  in  shutting  down  the  motor-generator  set : 

Disconnect  the  leads  to  the  generator  by  means  of  switches  and  circuit 
breaker  on  power  switchboard ;  move  the  generator  field  rheostat  handle  to  the 
position  showing  the  lowest  voltage  o])tainable ;  open  motor  main  switch ;  be 
sure  that  magnetic  holder  on  motor  starting  box  releases  the  lever  and  that  It 
returns  to  the  "  stop  "  position.  The  latter  will  not  occur  until  the  motor  gen- 
erator .set  slows  down  perceptibly.  This  is  due  to  the  counter-electro  motive 
force  of  the  set,  which  continues  to  energize  the  magnetic  holder  after  the 
current  is  "  cut  off  "  from  motor. 

Never  stop  the  set  by  releasing  the  lever  of  the  aiitomatic  starting  box  before 
opening  the  main  switch,  as  it  is  apt  to  burn  the  contacts  on  the  starting  box  and 
may  punctiu'e  the  insulation  of  the  field  windings. 

After  the  set  has  been  stopped,  wipe  off  all  oil  and  dust,  and  if  set  is  not  to  be 
again  operated  within  a  reasona)>le  period  of  time,  the  canvas  case  should  be 
placed  over  it  so  as  to  protect  the  machine  from  dampness  and  dust. 

Care  and  attention  of  commutators. — The  commutator  surface  should  be  kept 
clean  and  smooth.  A  cloth  with  a  little  vaseline  may  be  nsed  to  lubricate  and 
clean  it,  care  being  taken  that  it  be  wiped  clean  after  every  treatment. 

A  rough  commutator  may  be  smoothed  by  tising  No.  00  sandpaper  held  against 
it  midway  between  the  brushes  while  the  armature  is  rotating  slowly.  Before 
applying  the  sandpaper,  the  brushes  should  be  raised.  Never  apply  emery  cloth 
to  a  comnuitator. 

A  commutator  that  is  eccentric  or  that  has  high  spots  should  be  turned  true. 
As  the  turning  tool  does  not  leave  a  sufficiently  smooth  surface  for  proper  ojiera- 
tion,  No.  00  sandpaper,  mounted  on  a  wooden  block  fitted  to  the  conunutator, 
should  be  applied  until  the  surface  is  perfectly  smooth.  Inspect  the  surface  to 
see  that  the  coi)per  has  not  been  burred  over  from  segment  to  segment,  and 
remove  by  a  scraper  any  particles  of  copper  which  might  be  found  between  the 
segments. 

Not  infrequently  flat  spots  on  the  comnuitator  are  started  by  a  flash-over 
developing  from  an  open  circuit  in  windings,  or  are  caused  by  a  dirty  conunu- 
tator. These  flat  spots  passing  under  the  brushes  give  rise  to  loud  noise  and 
objectionalile  sparking.  They  can  not  be  removed  properly  by  sandpaper,  and 
when  they  develop  the  commutator  should  be  turned,  as  described  above.  The 
hinsh  holders  should  be  so  located  on  the  brush  studs  that  the  rings  of  contact 
ma<le  by  the  carlmns  of  one  set  of  brush  holders  overlap  those  made  by  the  next 
adjacent  set. 

Jirnshes. — The  copper  plating  on  th(>  brushes  should  be  kept  cut  back,  so  as 
not  to  come  in  contact  with  the  connnulator.  A  siiinll  amount  of  conunutator 
wear  will  be  compensated  for  in  the  brush  holder  by  the  brush  slipi)ing  througli 
the  holder.    Large  conunutator  wear  should  be  compensated  for  as  follows: 

Reset  the  brushes  in  the  following  mannei- :  ri;ice  a  narrow  strip  of  paper 
around  the  commutator,  having  the  two  ends  meet.  After  I'cnioving  this  paper 
di\i(l('  It  in  as  many  i»arts  as  there  are  jioles.  marking  e;icii  division,  then  place 
the  strip  around  the  (■<tiinnutator,  sticking  it  on  willi  a  lilllr  siicllac  ;it  several 
points.     In  this  way  (lie  i»r(tper  spacing  of  liir  hrnshcs  is  ohiained. 

Throw  the  tension  spring  back  as  far  as  possible.  Turn  the  brush  h(»lders  on 
the  studs  until  the  brushes  are  I'adial.     Then  claniji  the  brush   holders  in  this 

(432) 


Requisitions  and  General-Maintenance  Regulations. — Chapter  10.         11 

po.sition.  Tlic  distance  between  the  holders  and  the  commutator  surface  in  all 
ras«'s  sliduld  he  approximately  the  same,  and  should  in  no  case  be  nearer  th»* 
(•(•niniutator  than  three-sixteenths  of  an  inch.  If  for  any  reason  the  brushes 
of  any  stuil  do  not  come  on  the  lines  of  the  strip  of  paper  wrapped  around  the 
connuutator,  move  that  stud  so  that  the  brush  will  come  on  the  line.  Now 
si)rinfj;  the  tension  sprinj^  Inick  into  place  and  ai)ply  the  proi)er  tension.  In  all 
cases  such  a  pressure  should  be  applied  as  to  jrive  appntxiniately  1  pound  per 
S(|uare  inch  of  brush  contact. 

By  using  a  tine  jii'ade  of  sandpaper,  the  brushes  sliould  be  sanded  to  the  curv- 
ature of  the  commutator.  Cut  the  sandpaper  into  strips  a  trifle  wider  than  one 
l»rush.  Place  this  under  the  brush  with  the  smooth  side  next  to  the  commutator, 
then  draw  the  sandpaper  back  and  forth  imder  the  brush,  keeping  it  against 
the  commutator,  so  that  the  brush  will  have  the  curvature  of  the  comunitator. 
End  the  sanding  process  by  drawing  the  paper  under  the  brush  holder  several 
times  in  the  direction  of  rotation  only.  Blow  out  all  carbon  dust  and  wipe  off 
the  connections,  special  care  being  taken  to  .see  that  the  connuutator  is  cleaned. 

Spai-kirif/  may  be  caused  by — 

(a)  Brushes  not  being  set  at  the  proper  place. 

( b )  The  brushes  not  being  fitted  to  the  commutator. 

((■)   The  bru.shes  not  having  the  proper  pressure  on  the  commutator. 
((/)    S(tme  brushes  having  excessive  pressure,  and  thus  taking  more  than  their 
share  of  the  current. 

(c)  The  brushes  being  burned  on  the  ends,  due  to  excessive  overloads  having 
occurred. 

(/)   A  rough  connuutator. 

((/)   A  high,  low,  or  loose  connuutator  bar. 

(/O   High  mica. 

(0   Oily  or  dirty  connuutator. 

(j)  Open  circuit  in  the  armature  winding  or  loose  connections  between  the 
armature  conductors  and  the  comniutat(jr  tangs. 

Hot  or  glowing  bru.shes  are  due  to  excessive  current  density  at  the  brush 
contact  surface,  caused  by  (jverloads,  incorrect  brush  position,  dirty  commutator, 
or  the  picking  up  of  copper.  The  picking  up  of  copper  embeds  in  the  surface 
of  the  brush  small  particles  of  copper,  thus  causing  a  low  resistance  path 
between  the  brush  and  the  commutator,  and  permitting  a  heavy  flow  of  current 
at  this  point,  thus  developing  glowing  brushes.  This  difficulty  may  be  removed 
by  drawing  a  piece  of  fine  sandpaper  across  the  contact  surface  of  the  brush. 

OverJuathif/  of  the  commutalor  may  be  due  to — 

(a)  Overloads. 

(6)   Excessive  brush  pressure. 

(c)   Sparking.      (See  general  subject  "Sparking.") 

Overheating  of  beariiu/s  may  be  due  to — 

(«)   Defective  alignment. 

(b)  Failure  of  oil  rings  to  revolve. 
{(■)  Rough  bearing  surfaces. 

{(I)   Bent  shaft. 

(c)  Not  enough  oil. 
(/)    Poor  grade  of  oil. 

(f/)   End  thru.st.  due  to  improper  leveling. 

(h)  Large  unbalaneed  magnetic  pull,  due  to  the  armature  not  being  central 
with  the  frame:  generally  resiUting  from  excessive  journal  wear. 


(433) 


12  Signal  Corps  Manual  No.  3.— Chapter  10. 

Throwing  or  leaking  of  oil  is  frequently  caused  by — 

(a)  The  oil  being  too  high  in  the  bearings. 

(b)  The  plug  which  is  screwed  into  the  oil  well  drain  not  being  tight. 

(c)  Shaft  not  being  level. 

Excessive  field  heating. — If  one  of  the  field  coils  is  warmer  than  the  others  the 
trouble  will  usually  be  found  to  be  a  short  circuit.  This  may  be  detected  by 
taking  the  voltage  drop  across  the  terminals  of  each  individual  coil. 

An  unloaded  motor  generator  should  start  when  the  lever  of  the  motor  starting 
box  is  in  contact  with  the  second  or  third  segment.  If  this  does  not  happen,  the 
trouble  may  be  due  to  an  open  circuit  in  the  field  or  armature  windings,  in  the 
starting  box,  or  imdue  friction  in  the  set. 

While  the  foregoing  pertains  principally  to  motor  generator  sets  with  direct- 
current  motors,  it  applies  to  motor  generator  set  having  alternating-current 
motors,  except  that  with  the  sizes  usually  installed  by  the  Signal  Corps  the 
motor  is  started  by  merely  closing  a  D.  P.  S.  T.  knife  switch,  no  auxiliary 
starting  apparatus  being  necessary. 

POWER  SWITCHBOARD  MAINTENANCE. 

All  switch  parts  should  be  kept  bright  and  clean,  and  care  should  be  taken  to 
see  that  all  nuts  are  tight  and  that  no  corrosion  exists  at  the  contacts. 

The  voltmeter  switch  should  be  inspected  frequently,  to  see  that  all  con- 
tacts are  positive.  Particular  attention  is  invited  to  the  necessity  for  regu- 
lar inspection  of  all  connections  in  the  rear  of  these  switchboards,  in  order 
that  trouble  which  might  arise  from  loosening  of  parts  or  similar  causes  may 
be  anticipated.  While  particular  care  is  taken  by  the  Signal  Corps  to  avoid 
the  possibility  of  the  corrosion  of  terminals,  (hie  to  the  use  of  .soldering  salts 
and  to  other  causes,  it  is  well  to  examine  the  lugs  frequently  during  the 
first  year's  operation,  since  trouble  from  this  cause  may  occur.  It  is  pointed 
out  that  a  high  resistance,  such  as  might  be  caused  by  a  defective  lug  in  tlie 
circuit  of  the  telephone  storage  battery,  may  be  the  cause  of  cross-talk. 

Separate  fuses  for  all  circuits  should  be  kept  on  hand  in  ample  quantity,  and 
if  at  any  time,  through  a  series  of  accidents,  a  number  of  fuses  have  been 
blown  and  the  reserve  supply  becomes  low,  special  requisition  should  be 
sent  in  without  delay,  since  only  under  conditions  of  grave  emergency  should 
inclosed  fuse  terminals  be  bridged  by  an  open  wire  link.  If  this  must  be 
done,  connection  should  be  made  in  the  rear  of  the  board.  When  such  a 
fuse  is  blown,  the  switchboard  is  likely  to  be  defaced  in  a  manner  which  is 
beyond  remedy,  aside  from  the  possible  damage  to  the  terminals.  It  is  intended 
that  the  .supply  of  fuses  should  be  of  sufficient  magnitude  to  make  such  a 
contingency  extremely  unlikely. 

DRY  BATTERIES. 

As  stated  iti  chapter  1,  all  cells  furnished  by  the  Signal  Corps  bear  the 
date  of  manufacture,  and  no  cell  except  the  reserve  typ<>  should  he  installed 
for  .serious  work  that  is  more  than  18  months  old,  unless  test  with  the  am- 
meter and  voltmeter  shows  that  it  has  a  voltage  of  at  least  1  or  that  the 
ampere  reading  will  he  at  least  2. 

The  cells  should  be  stored  where  the  temperature  is  moderate,  dry,  and 
oven.  When  installed,  care  should  be  taken  to  keep  the  cardboard  covers 
as  (hy  as  possilile;  also  to  keep  the  cells  separated  from  each  other  by  a 
slight  air  space. 

(434) 


Requisitions  and  General-Maintenance  Regulations. — Chapter  10.         13 

TOOLS    FOK    MAINTENANCE    PURPOSES. 

Tool  kits  and  line  construction  tools  appropriate  with  size  and  nature  of 
systems  will  be  issued  for  nialiitenance  of  post  telephone  aii<i  sniall-ariiis 
target  range  signaling  systems  at  interior  posts. 

Signal  officers  should  use  carefid  .judgment  in  the  assortment  of  tools  held 
at  a  post  for  this  puri)ose  and  should  take  steps  to  have  "  turned  in  "  to  a 
Signal  Corps  supply  depot  tools' that  appear  to  be  superfluous. 

MAINTENANCE    OF    FIELD    EQUIPMENT. 

liicszer  tvhen  in  constant  use. — As  soon  as  possible  after  the  daily  drill,  each 
chief  of  section  should  examine  his  service  buzzers  and  test  them  out  for 
trouble,  whether  or  not  they  have  been  in  satisfactory  condition  at  the  morning 
drill  or  not.  This  must  be  done  to  avoid  any  minor  faults,  such  as  loose  key, 
key  short-circuiting,  broken  connections  in  line  and  ground  circuits,  loose  con- 
nections to  receiver  and  transmitter,  etc.  This  test  should  be  made  in  con- 
junction with  the  circuit  through  cart,  by  plugging  in  one  buzzer  on  the  cart, 
the  other  to  ground  through  field  wire  on  drums,  making  certain  that  the 
brushes  on  each  drum  make  good  connections  to  their  commutators. 

Learn  how  to  attach  reserve  cells,  which  may  be  necessary  when  Ever  Ready 
cells  can  not  be  obtained. 

The  receiver  and  transmitter  compartment  of  buzzers  issued  in  the  post 
should  be  lined  with  sheepskin  by  company  mechanics.  Buzzers  manufactured 
in  future  will  be  provided  for  in  this  respect. 

Wire  carts. — When  on  march  lubricate  axles  daily.  When  in  garrison  lubri- 
cate twice  weekly. 

Cart  chains  and  clutches  should  be  thoroughly  cleaned  at  least  once  per 
week.     When  cleaning  chains  replace  loose  or  broken  cotter  pins. 

Annually,  or  semiannually,  the  wire  carts  should  be  taken  apart,  thoroughly 
cleaned,  and  examined  for  minor  faults  that  will  develop.  They  should  be 
repainted  while  taken  down,  and  spare  parts  should  be  substituted  for  those 
badly  worn. 

In  gflrrison  the  carts  should  be  parked  in  sheds  such  as  Field  Artillery  use. 
If  it  is  impossible  to  shelter  the  carts  in  the  field,  the  cart  paulins  should  be 
spread  over  carts  and  secured  to  tongue,  mogul  springs,  and  wheels. 

If.  due  to  any  cause,  the  field  wire  has  been  reeled  up  on  the  drums  in  poor 
shape,  it  should  be  rewound  in  a  shipshape  manner,  as  otherwise  it  may  be  so 
loose  as  to  wrap  itself  around  the  cart  axle  at  the  next  drill. 

Cart  chains  of  obsolete  type  wire  carts. — When  in  constant  use  wipe  off 
chains  with  a  rag  and  then  apply  graphite  preparation  at  least  every  third  day 
and  oftener  if  the  chains  are  covered  with  mud. 

The  sprocket  chains  on  wire  carts  should  be  removed  and  thoroughly  cleaned 
at  least  once  in  three  months  and  more  often  if  constantly  in  use  at  maneuvers. 
After  removing  the  chain,  wash  off  all  old  grease  and  accumulated  sand,  using 
a  stiff  brush  and  gasoline  or  kerosene.  When  apparently  clean,  coil  the  chain 
in  a  pan  or  bucket,  covering  it  with  kerosene  or  gasoline  and  allow  it  to  stand 
for  several  hours  if  time  will  pernnt.  If  the  chain  has  been  cleaned  in  kero- 
sene, it  should  finally  be  rinsed  with  gasoline,  which  will  then  evaporate  in  a 
few  minutes,  leaving  the  chain  clean  and  dry.  Next  prepare  a  lubricant  con- 
sisting of  the  following  ingredients:  Ten  parts  of  the  best  beef  tallow,  two 
parts  of  heavy  oil,  and  one  part  of  powdered  graphite ;  these  ingredients  to  be 
heated  in  a  heavy  pan  sufficiently  for  the  lubricant  to  flow  freely,  but  not  enough 
heat  to  draw  the  temper  of  the  steel.     The  chain  should  be  coiled  in  the  pan  and 

(435) 


14  Signal  Corps  Manual  No.  3. — Chapter  10. 

allowed  to  remain  in  the  warm  lubricant  for  at  least  half  an  hour.  This  process 
insures  that  the  lubrit-ant  will  penetrate  every  part  of  the  chain,  includiufi  the 
inside  hearinjj;  surfaces  of  the  bushings  and  rollers. 

When  the  chain  has  been  removed  for  any  reason  it  should  be  replaced  with 
the  same  side  toward  the  sprocket,  so  that  it  will  run  in  the  same  direction  as 
before  removal. 

Keep  pairs  of  sprockets  in  perfect  alignment. 

Wire  pikes. — Examine  daily  the  hooks  on  wire  pikes  in  use  and  replace  those 
badly  worn.  Worn  hooks  tear  insulation  from  field  wire,  and  are  frequently 
jerked  from  the  hand. 

Field  irire. — When  field  wire  on  which  the  insulation  is  defective  is  used  on 
damp  ground,  moisture  causes  the  wire  to  rust  and  break  easily.  Keep  the 
insulation  repaired  daily  by  use  of  tape. 

Leather. — Do  not  experiment  with  the  preservation  of  leather.  Obtain  and 
follow  strictly  the  instructions  issued  by  the  Ordnance  Department  for  clean- 
ing and  preserving  leather.    Leather  is  often  ruined  by  use  of  too  much  oil. 


(i43aj 


Chapter   1 1 . 

LONG  SUBMARINE  CABLES;  SUBMARINE  TELEGRAPHY;  TESTS  OF 
SUBMARINE   CABLES. 

The  oonstniction,  characteristics,  and  manner  of  splicing  submarine  cable 
employing  Iiidia-rubber  compound  as  an  insulating  medium,  are  descrii)ed 
in  chapter  4  of  this  manual,  consequently  it  will  not  be  repeated  in  this 
chapter  because  what  has  been  stated  in  this  connection  ai)plies  also  to  long 
submarine  cables. 

It  is  believed  that  the  Signal  Corps  laid  the  first  long  submarine  cable  that 
had  rubber  compcanul  for  insulation  instead  of  gutta-perrha.  The  cables  re- 
ferred to  are  the  submarine  cables  of  the  Washington-Alaska  Military  Cable 
and  Telegraph  System,  the  longest  single  stretch  of  which  is  between  Seattle 
and  Sitka,  approximately  1,()S5  miles.  This  cable  has  been  in  use  over  11 
years,  the  service  it  has  rendered  being  satisfactory. 

With  the  long  trans-Atlantic  cables  gutta-percha  is  employed  as  the  in- 
sulating medium  instead  of  rubber  compound  described  in  chapter  4.  (Jutta- 
percha  has  two  important  characteristics  which  reconunend  it  for  such  cables, 
one  is  that  the  deteriorating  effect  is  less  than  rubber  compound  provided  it 
is  kept  constantly  submerged,  and  the  other  is  that  it  will  better  withstand  the 
enormous  pressure  to  which  a  cable  is  sul)jected  in  very  deep  water.  With 
some  of  these  cables  each  insulated  conductor  is  wrapped  with  a  brass  ribbon, 
the  gutta-percha  being  first  covered  with  a  serving  of  tape  or  spun  thread. 
In  other  respects  the  cable  is  constructed' in  accordance  with  description  in 
chapter  4.  The  brass  ribbon  has  proved  effective  where  trouble  has  been 
occasioned  by  the  toredo,  a  submarine  boring  animal.  This  little  pest,  which 
exists  in  the  Atlantic  Ocean  and  eastern  seas,  forces  itself  between  the  steel 
armor  wires  and  bores  through  insulation  to  conductor,  thereby  causing  a 
ground  or  at  least  a  heavy  leak. 

SPLICING  GUTTA-PEUCHA  INSULATION   CABLE. 

In  splicing  cable  with  gutta-porcha  insulation,  the  armor  and  conductor  are 
treated  as  described  in  chapter  4,  but  the  gutta-percha  is  treated  quite  dif- 
ferently. Gutta-percha  is  the  sap  of  the  gutta  tree,  a  different  si)ecies  of  tree 
from  that  from  which  India  rubber  is  i)rocured.  In  splicing  cable  the  gutta- 
percha conductor  c-overing  is  treated  as  follows: 

The  ends  of  the  core  should  be  pared  off  after  the  conductor  has  been 
spliced  and  soldered,  as  the  exposed  surfaces  are  apt  to  be  affected  by  the 
heat  used  in  soldering  joint  in  conductor.  Next  clean  gutta-percha  ends  and 
exposed  conductor  by  wiping  with  a  clean  rag  soaked  in  naphtha.  Oently 
warm  conductor  by  means  of  llame  of  spirit  lanqi,  great  care  being  taken 
to  not  burn  or  injure  the  gutta-percha.  A  stick  of  Chatterton  compound  which 
has  been  warmed  while  the  above  operation  was  in  process  is  now  rubbed 
over  the  conductor  and  that  which  adheres  to  conductor  is  smootheil  over 
to  a  thin  layer  by  means  of  a  warmed  iron.  The  spirit  lamp  is  then  used 
to    warm    evenly    and    slowly    the    gutta-iiercha    for    about    2    inches    on    each 

(437)  1 


2  Signal  Corps  Manual  No.  3. — Chapter  1 1 . 

side  of  the  jointed  coiKluotiir.  When  sufficiently  warmed  tlie  two  ends  are 
gradually  drawn  toward  each  other  (by  means  of  the  fingers,  which  should 
he  slightly  moistened  to  prevent  sticking)  until  about  one-half  inch  apart.  By 
the  same  i^rocess  one  end  is  then  drawn  down  to  a  thin  tilm  and  the  other 
drawn  over  so  as  to  lap  over  the  former.  In  drawing  the  gutta-percha  the 
conductor  should  be  revolved  backwards  and  forwards  between  the  fingers  to 
insure  drawing  evenly. 

The  joint  in  the  gutta-percha  is  then  kneaded  together  with  the  finger  and 
thumb  and  smoothed  down  with  a  warm  iron.  The  joint  thus  far  completed  is 
then  allowed  to  cool.  After  cooling  it  is  roughened  with  a  knife  and  then 
slightly  warmed  with  a  spirit  lamp  preparatory  to  treating  lightly  with  Chat- 
terton  compound  for  adhesive  purposes.  After  treating  with  Chatterton  com- 
pound the  joint  is  covered  with  a  thin  sheet  of  gutta-percha  which  has  been 
warmed.  This  covering  is  kneaded  into  place  with  finger  and  thumb  and 
smoothed  with  warm  iron.  Another  layer  of  sheet  gutta-percha  is  similarly 
placed  after  first  layer  has  been  treated  with  Chatterton  compound.  The  latter 
layer  should  extend  approximately  1  inch  beyond  the  first  layer  on  each  end  of 
joint.  In  applying  the  sheet  gutta-percha  great  care  should  be  exercised  to 
work  out  all  air  between  layers.  The  gutta-percha  joint  completed,  it  should 
be  thoroughly  cooled  l)y  pouring  cold  water  over  it  and  then  allowing  it  to  stand 
in  cool  air  for  a  reasonable  period  of  time.  The  joint  should  then  be  tested,  and 
if  satisfactory,  jute  or  thread  servings  and  armor  replaced,  as  described  in 
chapter  4  of  this  manual. 

LAYING  SUBMARINE  CABLE. 

In  laying  a  long  submarine  cable  it  is  ordinarily  paid  out  over  a  sheave  at 
Stern  of  vessel,  but  in  swift  currents  of  coast  waters  the  Signal  Corps  has  found 
it  more  satisfactory  to  pay  the  cable  out  over  sheaves  located  in  the  bow.  In 
deep  water  where  the  cable  will  sink  without  danger  of  coming  in  contact  with 
the  propellers  it  is  paid  out  over  the  "  bow  sheaves."  These  sheaves  are  per- 
manently located  in  extreme  bow  of  vessel  and  are  15  inches  in  diameter  (at 
bottom  of  groove)  on  the  cable  ship  Cyrus  W.  Field.  If  the  water  is  quite 
shallow  so  that  cable  will  extend  more  or  less  horizontally,  it  is  run  from  reel 
over  a  sheave  20  inches  in  diameter,  located  at  end  of  a  boom,  the  boom  being 
at  right  angles  to  ship's  length  and  extending  over  ship's  side  from  the  fore- 
mast. With  the  boom  and  (-able  on  upper  side  of  current,  the  ship  will  .swing 
away  instead  of  into  cable  and  the  course  of  ship  can  easily  be  controlled. 

The  advantage  of  paying  the  cable  out  over  the  "bow  sheave"  or  sheave  at 
end  of  boom  is  that  .stern  of  boat  can  always  be  turned  in  order  to  head  in  right 
direction  against  any  tide  or  current ;  and  while,  no  doubt,  the  cable  is  bent  at  a 
.shorter  radius  than  when  it  is  paid  out  over  stern  .sheave.s,  in  some  harbors 
and  coastal  waters  perfect  control  of  cable  ship  is  of  paramount  importance. 
A  cable  paying  out  over  stern  has  an  effect  similar  to  an  anchor  made  fast  to 
vessel  at  that  point,  as  a  tight  cable  in  this  position  prevents  the  stern  of  vessel 
from  .swinging  freely  in  answer  to  rudder,  thus  i»n'venting  accurate  steering. 
On  the  open  si-a  on  long  lines  (his  is  not  so  important,  as  no  swift  currents  are 
encountered  and  sliarj)  (urns  do  not  have  to  be  made. 

When  cable  is  being  laid,  electrical  measuring  insli-unients  are  so  coiniected 
III  the  ciihle  IhnI  sIkiuIiI  a  fauil  develoii  il  could  he  detecled  immediately.  Cable 
ship  pay-out  iiiiichinery  is  fitted  with  (»ne  uy  more  suitahle  friction  brakes  in 
onh-r  th;it  lahle  or  grajtnel  drag  line  will  not  pay  out  too  rapidly  and  that  strain 
on  t  hem  nia.\   he  eont  I'olled. 

(4.38) 


Long  Submarine  Cables,  Telegraphy,  and  Tests. — Chapter  II.  3 

When  laying  long  suhniarine  <'jil)los  more  elaborate  apparatus  is  necessary, 
because  in  very  deep  water  the  cable  is  subjected  to  severe  strain  when  being 
laid  or  taken  up  for  repairs  and  the  cable  ship  should  be  capable  of  storing  in 
its  tanks  or  hold  many  miles  of  cable.  The  reader  can  form  an  idea  of  the 
strain  on  cable  to  be  encountered  when  consideration  is  given  the  fact  that  not 
infrequently  cable  is  located  and  raised  in  water  2..5()0  fathoms  (1.^.0()0  feet) 
deep. 

In  view  of  the  fact  that  the  Signal  Corps  is  sometimes  called  upon  to  lay 
short  cables  in  shallow  waters  by  improvised  means,  an  account  of  method 
employed  in  laying  a  cable  in  Laguna  de  Bay,  near  Manila,  P.  I.,  may  prove 
useful.  The  cable  was  coiled  in  a  large  casco,  or  lighter,  the  coil  being  oblong 
(about  24  by  16  feet).  Starting  on  the  outside,  it  was  coiled  snugly  inward  to  a 
diameter  of  about  4  feet,  the  man  guiding  it  going  around  in  a  left-handed 
direction,  the  helpers  squatted  around  keeping  the  coil  closed  in  tightly  together 
as  the  cable  came  down  from  above.  A  wooden  cone  was  erected  in  the  center 
to  the  height  the  pile  was  to  reach,  the  edges  and  corners  being  well  rounded 
off  to  prevent  the  cable  catching  as  it  paid  out.  In  coiling  inward  the  cable 
coils  were  carried  up  snugly  against  each  other,  and  then  the  cable  was  carried 
radially  across  the  lower  layer  (flake,  it  is  called)  and  another  flake  begun  at 
the  outer  edge.  If  much  cable  is  to  be  put  on,  narrow  strips  of  wood  (called 
feathers)  are  laid  along  the  piece  of  cable  carried  straight  across.  Close  and 
careful  coiling,  especially  in  the  lower  flakes,  is  necessary. 

Sheaves  were  lashed  in  proper  places  to  carry  the  cable  up.  first  over  the 
center  of  the  cone  and  then  aft.  Near  the  stern  the  cable  passed  under  a  hori- 
zontal roller,  or  '"  fair  lead,"  and  means  were  provided  to  press  a  timber  against 
the  cable  here  to  pinch  it  and  put  on  the  necessary  friction  to  prevent  its  paying 
out  too  rapidly.  The  necessary  testing  apparatus  was  installed,  and  the  casco 
towed  by  one  of  the  gunboats  used  on  the  lake.  The  end  of  the  cable  was 
carried  ashore  in  two  small  boats,  one  buoying  it  between  the  casco  and  the 
boat  nearest  shore. 

This  can  be  done  when  distance  to  shore  is  short,  but  where  the  distance  is 
considerable  it  is  necessary  to  lash  two  or  more  boats  together  forming  a  raft, 
on  which  suflicient  cable  is  coiled  to  reach  the  siiore.  The  raft  is  towed  to  the 
shore  by  a  small  steam  or  gasoline  launch,  paying  out  the  cable  from  the  raft  as 
it  is  towed. 

Care  must  be  exercised  to  avoid  kinks  in  the  cable.  This  can  always  be 
avoided  by  placing  sufficient  strain  on  the  cal)le  to  prevent  its  being  perpen- 
dicular in  the  water. 

The  end  ashore  having  been  properly  trenched  and  anchored,  paying  out 
was  begun.  Several  helpers  were  on  the  cable  coils,  handing  the  cable  up  as  it 
started  to  rise  and  looking  out  that  no  kinks  went  up.  An  average  speed  of 
2^  miles  an  hour  was  attained,  the  water  being  not  over  40  or  .50  feet  deep. 
When  the  end  was  Tanded  the  cable  was  trenched  about  3  feet  deep,  down  to 
low  water.  Above  high,  water  a  short  cross  trench  was  dug.  a  heavy  log  was 
buried  therein,  and  a  chain  lashed  to  it  and  the  cable.  This  constituted  a 
"  sand  anchor  "  to  prevent  the  end  of  the  cable  from  being  pulled  out  to  sea. 

The  best  way  to  electrically  secure  the  land  end  of  the  cable  is  to  run  it  into 
the  office  and  connect  the  conductor  directly  with  the  office  switchboard.  The 
next  best  is  to  splice  the  submarine  cable  to  lead-covered  underground  cable, 
the  latter  going  to  the  office. 

If  the  cable  landing  is  far  from  the  office,  and  the  cable  must  be  coiuiected 
with  a  land  line,  the  end  of  the  cable  should  go  into  a  cable  hut.  This  is  a 
small  structure  in  which  the  cable  comes  up  out  of  the  trench  and  is  secured 

(439) 


4  Signal  Corps  Manual  No.  3. — Chapter  1 1 . 

to  the  lightning  arrester,  tlie  hind  line  leading  out  from  there.  Great  care 
should  be  taken  in  properly  securing  the  cable  terminal  either  in  the  office  or 
cable  hut.  Bad  insulation  or  poor  connections  are  too  often  left  there,  inter- 
fering with  the  work  of  the  line  or  vitiating  the  tests. 

GRAPNELS. 

In  locating  cable  in  deep  water  an  apparatus  termed  a  "grapnel"  is  employed. 
These  grapnels  are  of  various  forms,  but  all  types  are  equipped  with  arms 
projecting  from  a  common  spindle.  The  grapnel,  or  a  series  of  them,  is  made 
fast  to  a  strong  line  and  dragged  over  the  ocean  bottom  at  right  angle  to 
route  of  cable.  About  5  fathoms  of  chain  is  made  fast  to  end  of  grapnel  and 
dragged  in  rear  of  grapnel,  as  a  means  of  making  it  follow  a  straight  course 
on  uneven  bottom.  In  addition  a  length  of  chain  between  grapnel  and  dragging 
line  is  used  to  prevent  chafing  of  line  in  advance  of  grapnel.  In  deep  water  a 
considerable  amount  of  dragging  line  is  in  contact  with  ocean  bottom. 

DYNAMOMETER. 

In  deep-sea  cable  work  a  most-important  apparatus  termed  "  dynamometer  " 
is  used  for  measuring  the  strain  imposed  on  a  cable  or  a  lii\e.  While  the 
operation  of  the  instrument  is  comparatively  simple,  experience  in  its  use  is 
required  before  one  becomes  proficient  in  determining  what  is  taking  place 
many  fathoms  below  the  cable  ship. 

In  dragging  a  grapnel  in  connection  with  bringing  a  submarine  cable  to  the 
surface,  the  dynamometer  is  used  to  determine  when  the  cable  has  been  caught 
by  the  grapnel.  Of  course,  if  the  grapnel  catches  on  a  coral  reef  or  ledge,  the 
effect  is  almost  the  same,  but  the  experienced  operator  will  readily  detect 
that  the  cable  has  not  been  caught.  On  imeven  ocean  bottom,  where  the 
grapnel  leaves  a  high  place,  taking  some  time  to  again  reach  bottom,  the 
dynamometer  quickly  transmits  to  the  experienced  operator  what  is  taking 
place,  and  more  line  is  rapidly  paid  out  or  the  ship  slowed  down. 

If  the  breaking  strain  of  cable  is  known,  it  is  highly  advantageous  to  know 
to  what  strain  the  cable  is  being  subjected  when  either  the  operation  of  laying 
or  recovering  is  in  progress.  The  dynamoiuet(M'  furnislies  this  information 
continuously. 

A  few  of  I  lie  most  iiniioi-lniit  features  of  laying  and  recovering  long  sub- 
marine cables  have  been  entered  in  the  foregoing,  but  the  ground  to  be  covered 
in  any  stiuly  of  this  subject  is  very  wide  and  interesting,  and  justice  can  not 
be  rendered  it  in  the  limited  si)ace  available  here.  For  further  information  the 
reader  is  i-el'erred  to  "Submarine  Cahle  Laying  and  Repairing,"  by  H.  D. 
Wilkinson,  M.  I.  K.  E.,  and  "  Sulmiaiine  Telegrai)hs,"  by  Charles  Bright, 
F.  n.  S.  E. 

SUBMARINE    TELEGRAPHY. 

Due  to  electrostatic  capacity  and  indiictive  effect  of  rubber-insulation  cable, 
apj)roximately  2.1  miles  is  the  limit  of  length  over  wliicli  audible  conversation 
can  he  ordinarily  transmitted  teleplKniically.  This  distanc(>  can  be  greatly  in- 
creased by  what  is  termed  "loading,"  which  means  that  inductance  is  assimi- 
lated in  the  circuit  at  one  or  more  points.  While  the  latter  lias  been  accom- 
plished in  medium  length  submarine  cables,  to  dale  it  is  inii)racl  icable  on  ex- 
tremely long  cables  such  as  those  used  for  trans-.\tlanl  ic  connnunication. 

On  all  cables  over  1!(M)  miles  in  length  the  retardation  of  the  signals  becomes  sd 
great    that   M(»rse  ajtparatus  is  at  a  serious  disadvantage;  consiM|uently  some 


(440J 


Long  Submarine  Cables,  Telegraphy,  and  Tests. — Chapter   11.  5 

inor(»  (lolicatc  form  of  receiving,'  iippiirjitus   is   iiocossary.     That  almost   univer- 
sally adopted  is  tlie  sipJion  recorder. 

A  description  will  first  be  jriven  of  tlie  operation  of  submarine  cables  wbere 
the  ordinary  Morse  telegraph  ajiparatus  is  employed.  This  des<'ription  will  ho 
followed  by  a  description  of  the  operation  of  submarine  cables  where  the  more 
sensitive  siphon  recorder  is  employed. 

SWITCIIROAIinS. 

If  practicable  the  cable  should  be  terminated  at  the  switchboard. 

A  .special  hlRh-insulation  .switchboard  for  cable  station.s  is  fiirnislied  by  the 
Signal  Corps  and  is  shown  diafrranmiatically  in  figure  11-1. 

The  cable  conductor  or  line  to  cable  hut  is  connected  to  the  upper  left  bind- 
ing post.  A  revolving  copper  strip  is  attached  thereto  and  the  bas(>  is  marked 
"Instruments,"  "Free,"  or  "Earth,"  corresponding  to  positions  of  the  strip. 


Fig.  11-1.— LONG    SUBMARINE    CABLE,    SWITCHBOARD. 
(441) 


6  Signal  Corps  Manual  No.  3. ^Chapter  1  1. 

This  is  a  laseful  arrangement  in  making  tests,  to  conform  to  instructions  from 
tlie  ship  or  distant  station. 

The  wire  to  ground  or  to  cable  leading  to  the  other  station  (in  case  this  sta- 
tion is  a  way  office)  leads  to  upper  right-hand  binding  post.  A  disk  lightning 
arrester  is  connected  with  a  binding  post  leading  to  groimd  wire.  Tlie  other 
binding  posts  are  connected  with  ii>strument  leads  in  the  usual  way,  and  cir- 
cuits are  pegged  in  as  on  the  land-line  switchboards.  All  openings  in  the 
wooden  case  not  occupied  by  wires  sliould  be  securely  pegged  up.  The  wooden 
case  and  glass  cover  protect  the  hard-rubber  base  against  dust  and  moisture. 
During  tests,  when  insulation  must  be  carefully  guarded,  a  small  cup  of 
chloride  of  calcium  may  be  set  in  the  closed  case  to  absorb  all  moisture. 

LIGHTNING   ARKESTERS. 

The  disk,  plate,  point,  and  spiral  arresters  are  all  "  jump  "  arresters,  when 
the  lightning  jumps  from  plates  of  metal  or  carbon,  or  from  points  or  spiral 
connected  with  the  line  to  a  carbon  or  metal  plate  connected  with  the  ground 
wire.  The  metal  ones  are  liable  to  be  fused  by  a  flash  and  should  always  be 
carefully  examined  to  see  if  the  line  is  accidentally  grounded  by  them.  Carbon 
dust  is  liable  to  cause  similar  trouble  in  those  made  of  carbon  plates  separated 
by  thin  perforated  mica.  The  fuse  lightning  arresters,  in  which  a  short  piece 
of  fusible  wire  is  in  circuit  with  the  line,  arrest  the  flash  by  melting  off.  This, 
of  course,  opens  the  line,  and  spare  ones  should  always  be  ready  to  replace  the 
burned  ones.  The  delicate  ones  mounted  on  mica  strips  with  metal  ends  need 
to  be  especially  watched.  When  the  line  becomes  open  or  is  grounded,  the 
lightning  arresters  should  at  once  be  carefully  inspected. 

GROUND    CONNECTIONS.  . 

These  should  be  made  with  special  care  at  cable  stations. 

Where  practicable  this  connection  should  be  made  by  securely  soldering  to 
at  least  three  or  four  of  the  armor  wires  of  the  cable  a  coi)per  conductor.  102 
mils  diameter  or  larger,  leading  it  in  a  neat  and  permanent  manner  to  switch- 
board. Whore  plate  ground  connections  are  used,  the  plate  should  be  copper,  of 
at  least  5  S(iuare  feet  surface,  with  the  ground  wire  solderetl  securely  to  it. 

OFFICE   WIHIXC. 

In  tropiia!  ciinialcs  it  has  been  found  that  the  ordinary  iiarafilnod  office  wire 
is  worthless  for  gtxtd  insulation.  In  cable  stations  nothing  should  be  used  hut 
heavily  rubber-covered  wire.  The  cable  core  itself  is  a  type  of  the  insulation 
which  the  wire  should  have.  It  will  pay  to  put  up  the  wire  with  extra  care, 
using  porcelain  cleats  and  knobs;  never  fasten  a  wire  with  any  of  the  ordinary 
staples,  whicli  in  a  majority  of  instances  will  be  bangiMl  down  on  the  insula- 
tion, cutting  into  it  and  causing  Iiad  leaks,  which  are  most  baffiing  to  find. 

INSTRUMENTS    lOK    CAIU.E    WORKING. 

<  Ml  cables  up  to  KK)  miles  in  length  the  conditions  for  successful  working  do 
not  (Icpiirt  sudicienlly  fi-oin  those  ol'  land  lines  to  i>revent  the  use  of  ordinary 
.Morse  inslrunients.  The  ordinjiry  closed-circuit  Morse^  may  be  used  as  long  as 
no  incipient  faidt  exists.  I'.ut  with  the  current  constantly  on,  the  least  faidt 
in  the  insulafion  is  rapidly  made  greater  by  electrolytic  action,  and  a  br<>ak- 
down  soon  occurs,  l^'or  this  reason  the  Signal  Corps  uses  the  open-circuit 
.system  of  Morse  telegraph. 

(442) 


Long  Submarine  Cables,  Telegraphy,  and  Tests. — Chapter   11.  7 

A  .«!implifie<I  diapram  of  the  open-circuit  connections  at  a  station  is  jriven  in 
figure  11-2. 

As  will  he  seen  in  diafrrani,  the  line  oome.s  to  the  relay,  thence  to  ho<ly  of  key, 
thence  to  back  contact  of  key,  and  to  the  ground.     This  is  the  receiving  posi- 


LoobI  Bdtfery 


r 


O      0^^ 

^oundeK 


Cdb/e 


-ff 


Relay 


\    y/Tey 


_=_  Mziin  BBffer-y 


Fig.  11-2.— SUBMARINE  CABLES,  MORSE  OPEN  CIRCUIT  TELEGRAPH Y,  CONNECTIONS. 

tion.  and  the  current  from  distant  stations  will  operate  the  relay.  When  key  is 
depres.sed,  the  back  contact  is  broken  and  the  front  contact  made;  this  will 
cause  the  home  battery  to  be  in  the  circuit  and  operate  the  relays. 

Special  care  must  be  taken  not  to  screw  key  so  close  that  both  front  and  hack 
contacts  touch.     This  would  short-circuit  the  battery  and  speedily  ruin  it. 

The  polarized  relay  has  two  bobbins  or  pairs  of  magnets  facing  each  other, 
with  the  armature  between  them.  A  permanent  magnet  supporting  the  bobbins 
or  in  the  base  gives  the  cores  of  the  magnets  polarity  opposite  to  that  of  the 
armature,  so  that  the  current  coming  in  one  direction  tends  to  send  the  relay 
tongue  to  the  front  contact,  and  coming  in  the  other  to  the  back  contact.  Ad- 
justment is  made  with  top  screw,  as  the  relay  tongue  tends  to  be  more  or  less 
strongly  held  by  the  permanent  magnet  on  the  back  contact,  corresponding  to 
spring  adjustment  of  the  ordinary  relay.  The  screws  controlling  the  magnets 
seldom  need  any  adjustment.  Care  should  be  taken  that  the  armature  does 
not  jam  against  the  ends  of  magnets. 

A  polarized  relay  is  u.sed  for  two  reasons:  First,  it  is  more  sensitive  and  can 
be  worked  on  less  cm-rent;  second,  on  account  of  the  large  capacity  of  cables 
as  compared  with  land  lines,  the  current  first  charges  the  cable  when  the  key 
is  depressed,  the  cable  then  discharges  when  key  is  released,  and  a  momentary 
current  rushes  back  through  the  relay.  An  ordinary  relay  would  give  a  "  kick  "' 
corresponding  to  this,  but  the  polarized  relay,  responding  to  the  direct  current 
only,  is  not  affected  by  this  momentary  discharge  current  in  the  opposite  direc- 
tion, and  the  signals  are  not  "  chopped." 


46581°— 17- 


-29 


(443) 


8 


Signal  Corps  Manual  No.  3. — Chapter  I 


The  key  has  a  back,  middle,  and  front  contact,  as  sliown.  (lie  battery  being 
put  to  line  only  wlien  key  is  depressed.  The  battery  used  is  some  form  of  good 
open-circuit  battery  like  the  Gonda,  or  large-sized  dry  batteries. 


DOLTBLE-CIRRENT    WOKKINll. 

Wlien  the  cable  apprei-ial)ly  exceeds  1»>0  iiiilcs  in  lengdi  it  begins  to  work 
lieavily  on  account  of  the  appreciable  length  of  time  it  takes  for  the  cable  to 
tharge  and  discharge.  A  modification  of  the  simple  open-circuit  method  of 
working,  just  described,  must  be  made.  This  is  called  the  double-current 
method,  and  in  principle  consists  in  connecting  an  additional  main-line  battery 
to  the  back  contact  of  the  key  with  polarity  opposite  to  the  main-line  battery 
connected  to  front  contact.  These  batteries,  by  alternately  connecting  opposite 
poles  to  line  as  the  key  is  up  or  down,  serve  to  discharge  the  line  much  more 


'Sounder 


BscH  ConfdO^    _=_ 


_  fronf  Conf-acf 


Fig.  11-3. 


-SUBMARINE   CABLES,    MORSE    DOUBLE   CURRENT    TELEGRAPHY,    CONNEC- 
TIONS. 


I'aiiidiy  and  gi'cally  increase  the  speed  of  working.  A  simplified  diagram  of  tlie 
connections  is  given  in  figure  11-3. 

The  simple  change  to  make  it  a  plain  open-circuit  s(>t  appears  when  the 
switch  is  thrown  to  A.  AN'ilh  the  key  tm  tlie  back  coiitncl.  a  current  flows 
to  line  from  the  -f  pole  of  l)ack  contact  battery.  When  key  is  depressed  tlie  — 
pole  of  llie  front  contact  battery  is  connected  to  line.  The  polarized  relays 
are  so  connected  lliat  they  close  the  local  circuit  with  tronl  contact  battery 
to  line.  Connections  fui-  a  three-station  line  for  double-current  working  are 
shown   in  figure  11^. 

Without  a  switch  t\w  back  contact  batteries  would  soon  be  run  down.  As 
oiterators  are  accustomed  to  closing  the  key  with  the  ordinary  circuit-closer 
lever,  a  key  is  issued  by  the  Signal  (!orps  obviating  the  use  of  a  separate 
switch.  The  connections  are  so  arranged  thiil  llic  customary  movements  of 
the  switch  lever  will  make  the  correct  connections  for  the  double-current 
system.  (Hher  combinations  can  be  made  with  this  key  which  is  shown  in 
figure  11-5. 


(444) 


Long  Submarine  Cables,  Telegraphy,  and  Tests. — Chapter  II.  9 


fxoM  Station  6  rv  Statiom  C. 


Fig.  11-4.— SUBMARINE  CABLES,   MORSE  DOUBLE  CURRENT  TELEGRAPHY,  3-STATION 

CONNECTIONS. 


STtCl  TRUimiOW-  ALL  OTHtH 
PIDTS  SRAtJ  01  PnOS.  CKCIUL 

ALL  MEJAl  rouuiLO. 


SIO£  ELEVATION 

Fig.  11-5.— SUBMARINE  CABLES,   MORSE  DOUBLE  CURRENT  TELEGRAPHY,   KEY  USED 

BY    SIGNAL    CORPS. 
(445) 


10  Signal  Corps  Manual  No.  3. — Chapter  11. 

SINGLE-CURKEXT  OPEN-CIRCUIT  REPEATER   SETS. 
[See  fig.  11-G.     Fig.  11-7  is  a  simplified  diagram.] 

Mountoil  (Ml  a  small  table  top  are  the  following;  instnimenti=i :  Two  polarized 
relays,  -1.1;  two  soimilers,  BB;  two  open-circuit  keys,  CC ;  two  transmitters. 
I)D :  one  double  switch,  E. 

The  main  line  and  local  batteries  for  each  of  the  lines,  the  lines  themselves, 
and  the  earth  are  connected  to  the  binding  posts  marked  on  the  table.  These 
connections,  especially  those  of  lines  and  earth,  should  be  made  through  the 
switchboard,  lightning  arresters,  etc. 

POLARIZED     RELAYS. 

These  are  v«m\v  similar  in  relation  of  ]iarts  and  construction  to  the  square 
Western  Union  pattern  used  heretofore  on  the  Philippine  cables,  with  the 
addition  of  a  small  switch  F  (fig.  11-6)  on  each,  which  permits  the  local  to 
work  on  either  front  or  back  stroke.  If  the  sending  comes  reversed,  throw 
the  switch  to  the  other  button. 

AdjiLstmcnt. — The  lower  adjusting  screws  on  each  side  should  be  turned 
until  the  magnets  are  fairly  close  to  the  armature,  care  being  taken  not  to 
jam  them  against  the  armature.  The  relay  tongue  can  then  be  caused  to 
fall  over  to  one  side  or  the  other,  as  desired,  by  the  top  adjusting  screw.  The 
magnetic  retraction  corresponding  to  relay  spring  can  thus  be  made  strong 
t»r  weak,  as  desired.  For  repeating,  tlie  set  works  better  if  the  relay  tongue  has 
a  barely  perceptible  play. 

Before  substituting  the  repeater  set  for  the  two  office  sets  find  out  from  each 
operator  at  distant  ends  of  both  Nos.  1  and  2  lines  whether  zinc  or  carbon 
is  connected  to  the  front  contact  of  his  key.  Suppose  No.  1  says  zinc.  Connect 
up  several  cells  of  battery,  put  wire  from  carbon  in  "  earth  "  binding  post  of 
repeater  set.  Connect  two  cells  at  local  binding  posts  of  No.  1.  Then  tapping 
with  wire  from  zinc  on  line  No.  1  binding  post,  note  if  it  works  the  relay  No.  1. 
If  not,  move  the  upper  adjusting  screw  until  relay  tongue  just  falls  over  on 
the  other  contact,  and  it  should  then  work  it.  If  your  sending  conies  reversed 
on  the  sounder,  throw  the  relay  switch  F  (fig.  11-6)  onto  the  other  contact. 

Proceed  in  the  same  way  with  No.  2,  being- sure  to  tap  on  line  No.  2  binding 
post  with  the  wire  coming  from  same  pole  of  ycmr  experimental  battery,  as 
reported  by  distant  end  of  No.  2  as  going  to  line  through  front  contact  of  key. 

Now,  having  placed  the  table  in  position  and  run  the  wires  from  switchboard, 
batt:eries,  etc.,  to  the  proper  binding  posts,  place  the  switch  at  "  cut  "  and 
try  to  work  on,  say,  No.  1.  If  you  do  not  succeed,  reverse  the  wires  leading 
lo  main  battery  No.  1  binding  posts,  and  this  will  probably  send  the  current 
in  the  right  direction  to  work  both  your  own  and  the  distant  relay. 

Proceed  in  the  siime  way  with  No.  2  before  attempting  to  uune  the  main 
switcli  to  the  "  repeat  "  position. 

SOUNDERS. 

These  sliouM  bo  adjusted  with  as  little  play  in  the  lever  as  is  consistent  with 
sullicicnt    loudness. 


(446) 


Long  Submarine  Cables,  Telegraphy,  and  Tests. — Chapter 


11 


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<447) 


12 


Signal  Corps  Manual  No.  3. — Chapter  11, 


wtoA  Line 


Msat  ffepeajii  <j 


Weet  Mam     -=■ 
Dattsry       -^ 


As  shown  battery  at  terminus  of  East  line  is  connected  to  line.    This  closes  AVest  polar  relay 
which  connects  "  West  main  battery"  in  circuit  with  West  line. 

Fig.     11-7.— SUBMARINE     CABLES,     MORSE     TELEGRAPHY,    SINGLE     CURRENT     OPEN 
CIRCUIT   REPEATER  SETS,  SIMPLIFIED   DIAGRAM   OF  CONNECTIONS, 

TR.VN.SMITTEUS. 

Earli  of  tlipsp  lias  a  front  and  liaok  contact,  like  the  keys;  in  fact,  it  is  an 
open-circuit  key  worked  by  its  electro-magnet  in  the  local  circuit  with  the 
sounder.  For  s<>f>(l  repeating,  the  lever  should  have  barely  a  perceptible  play. 
Be  careful  that  the  armature  does  not  strike  the  masnet ;  this  would  prevent 
the  "  front  contact  "  from  being  made  at  the  contact  points  nearest  the  magnets. 

Having  made  the  various  adjustments,  throw  the  double  switch  from  "  cut "" 
to  "  repeat."    The  two  lines  should  then  work  into  each  other. 

Note  that  when  distant  station  or  key  of  repeater  set  is  working,  say,  on  line 
No.  1,  only  that  side  of  repeater  .set  should  be  working,  and  similarly  for  No.  2. 

If  operators  at  distant  ends  conii)lain  that  signals  are  imperfect,  note  if 
repeater,  relay,  and  transmitter  levers  are  set  to  work  extremely  close,  or  if 
the  adjustment  is  not  too  strong  on  the  relays.  Al.so  if  the  si)rings  in  the  trans- 
mitters jirc  iKil   loo  strong. 

Senders  on  lines  tied  logcthcr  iiy  rciiciiters  should  be  cautioned  (bat  light, 
jfi-ky  sending  is  paiiicularly  iiard  to  gel   tlu-ougb  reiu'aters  well. 

DKSCIUI'TIOX     OK     OI'KK.\TIO\     OK     OI'KX-CllU'nT     .SI  NMiK-crUUKXl"   UKl'E.VTlNd     SET. 

I  Sec  liK.   11 -(•..] 

First,  supiHise  distant  station  on  line  No.  1  is  working,  the  double  switch 
set  to  "rejiciil."  The  current  comes  in  line  No.  1  biinliiig  posl,  thence  to  \\  and 
4  to  right  bar  (tf  switch,  through  contact  H  to  7  and  S  on  left  transmitter. 
Ihrougb  lever  of  Iransmitler  to  back  contact  VI  and  18.  through  14  to  rel;iy 
at  l."t.  tinuiigii  reliiv  cdils  operating  (be  r(4ay  tongue,  (hen  out  at  1(5  through 
17  on  key.  tlirougb  budy  ul'  key  (<»  l.S.  1!»,  ;iiid  lid  lo  earth,  'riie  local  circuit 
being  closed  at  rel.-iy,  tlie  lociil  biittery  sends  in  a  current  tlirougb  binding 
posl.s  lociil  .No,  1.  Ilu'iice  lo  magnet  of  t  r.-msMiitlei'  through  10,  out  at    11,  tin-ougb 


(44S) 


I 


Long  Submarine  Cables,  Telegraphy,  and  Tests. — Chapter  11.  13 

SdUiHlcr  at  42  and  43,  tliroiisli  relay  local  imiiils  at  44  and  4.",  thonr-o  l)ack  to 
Icical  No.  1  battery.  When  the  local  current  passes  throufih  transmitter  magnet 
it  closes  the  front  contact.  This  permits  the  current  of  main-line  battery  No.  2, 
starting,'  at  i)in(linj^  post,  cominj;  to  transmitter  on  40,  to  front  contact  30  and  38 
tln-oufih  lever  of  transmitter  to  20,  then  to  2;").  to  switch  contact  23,  throujrh  24 
to  left  bar  of  .switch,  to  22,  21,  and  to  line  No.  2  binding,'  i)ost,  ont  to  line, 
working  the  instruments  in  that  line.  An  exactly  similar  thinj;  happens  when 
an  operator  in  line  No.  2  sends  a  current  tlirough  his  side  of  the  repeater  set. 

When  the  repeater  station  works  his  key  on  the  No.  1  side,  a  current  comes 
from  No.  1  main-line  battery  left  binding  post  to  the  front  contact  of  his  key 
throuKli  47.  thence  through  key  lever  to  body  of  key,  then  to  relay  No.  1  through 
17.  through  relay  and  out  to  line  No.  1  through  16,  15,  14,  13,  12,  8,  7,  G,  5,  4,  3, 
to  "  line  No.  1  "  binding  post,  and  out  to  line. 

Relay  No.  1  works  its  local  circuit,  causing  the  transmitter  to  repeat  into  line 
No.  2,  as  before  explained. 

When  switch  is  turned  to  "  cut,"  each  key,  relay,  and  the  transmitter  and 
sounder  in  local  circuits  work  independently  as  two  ordinary  open-circuit  sets. 

Two  small  resistance  coils  under  the  binird  are  arranged  t(t  shunt  the  sounder 
and  tiansuutter  magnets  of  each  set.  This  prevents  sparking  and  sticking  at 
the  local  relay  points. 

Notes  on  Efficient  JIorse  Wobkixg  of  Si'bmarixe  Cables. 


The  battery  power  used  in  working  Morse  over  a  submarine  cable  should 
be  as  low  as  possible,  for  the  protection  of  the  cable  itself,  as  w-ell  as  for  the 
reduction  of  the  retardation  effect  of  the  static  capacity  of  the  cable. 

The  batteries  at  each  station  shoiUd  be  inspected  frequently  and  care  taken 
that  there  is  no  corrosion  at  their  connections  and  no  creeping  of  salts  and 
that  every  connection  is  good  and  tight.  If  possible  they  should  frequently  be 
tested  for  voltage. 

RELAYS. 

Whatever  may  be  the  type  of  relay  in  use,  great  care  should  bo  taken 
in  making  the  adjustment  that  there  shall  be  no  stitfness  at  the  pivots  or 
trouble  from  dirty  contacts.  Trouble  frequently  occurs  through  rust  or  cor- 
rosion at  the  pivots  which  makes  the  sensitiveness  of  the  relay  very  irregular, 
requiring  more  current  to  operate  it  at  times  than  the  normal  amount. 

In  general,  polarized  relays  are  more  sensitive  than  the  ordinary  150-ohm 
relay  and  should  be  used  wherever  possible.  In  these  relays  the  magnets  are 
drawn  back  by  screws  attached  to  each  pair.  The  sensitlvenesss  of  the  relay 
of  this  type  is  increased  by  drawing  back  the  magnets,  but  at  the  same  time 
the  strength  of  the  action  of  the  armature  is  made  more  feeble.  The  adjusting 
screws  on  top  should  be  so  arranged  that  the  armature  tt)ngue  naturally  falls 
slightly  to  back  contact,  the  arriving  signal  pulling  it  to  front  contact.  In  the 
polarized  relay  it  should  be  remembered  that  magnetic  action  is  substituted 
for  the  .spring,  and  consequently  the  amcmnt  of  bias,  as  it  is  called,  is  i-egu- 
lated  by  the  adjustment  of  the  top  adjusting  screw. 

In  general,  when  the  two  lower  screws  controlling  the  magnets  are  once 
set  to  regulate  the  required  amount  of  .sensitiveness  they  should  seldom  be 
changed,  the  ordinary  adjustment  for  changes  in  line  conditions  being  made 
entirely  with  the  top  screw. 


(449) 


14 


Signal  Corps  Manual  No.  3. — Chapter  11. 


When  the  line  is  worljed  through  condensers  at  the  receiving  end  (fig. 
11-8)  the  top  screw  is  then  so  regulated  that  the  armature  tends  to  fall 
either  way  indifferently,  the  motion  of  the  tongue  to-and-fro  being  determined 
by  the  positive  and  negative  discharges  from  condensers  produced  by  the 
action  of  the  distant  key. 

The  object  of  placing  a  condenser  in  the  receiving  circuit  in  this  latter  method 
of  working  is  to  cut  off  the  action  of  earth  currents,  whicli  in  the  ordinary  open- 
circuit  system  in  some  cases  make  constant  changes  necessary  in  the  adjust- 
ment of  the  relays.  The  sliunt  placed  around  the  condenser  sliould  be  adjusted 
as  near  infinity  as  is  consistent  with  firm  signals,  to  prevent  troubles  from 
earth  currents  mentioned  above.  Except  at  infinity,  the  use  of  the  shunt  per- 
mits of  giving  more  or  less  bias  to  the  relay  tongue. 


HADLEY 


WRANGEIL 


Wrongel-Hadley  Coble 


6OOohmi-30mf. 


fblahzai  Rela/ 
Coble  Set 


Fig.  11-8.— SUBMARINE     CABLES,     POLARIZED     RELAY     SET,     CONNECTIONS. 

The  magnets  of  the  receiving  relay,  if  of  the  ordinary  1.50-ohm  type,  should 
be  adjusted  well  up,  close  to  the  armature,  without  actually  touching  it,  and 
the  battery  gradually  reduced  until  there  is  no  sticking  of  the  signals  noticed, 
with  no  battery  on  the  line.  The  spring  should  be  "  turned  down  "  completely 
until  the  armature  falls  forward  against  the  front  contact,  and  then  again 
"turned  up"  until  the  armature  falls  against  the  back  contact,  and  then  again 
"  turned  up  "  the  least  bit  more  to  allow  a  margin  for  adjustmeiit.  If  a  relay 
of  the  Frier  self-polarizing  tyi)e  is  used,  the  attracting  magnet  should  be  kept 
close  to  the  armature,  and  the  other  magnet  adjusted  to  get  the  best  effect. 

In  an  o])en-cir(uit  Morse  system  on  cables  when  it  becomes  necessary  to  pull 
the  magnets  of  the  relay  away  from  the  armature,  it  shows  that  more  battery 
is  being  used  tlcin  is  reciuired.  This  battery,  therefore,  should  be  inunediately 
cut  down  iinil  ihe  magnets  adjusted  close  to  the  armature,  as  above  mentioned. 

I'UOrEIt     TOt'CII     TO     KEV. 

Morse  working  (Ui  cables  re(|uires  a  different  touch  froTU  that  needed  on  siiort 
land  lines.  Many  o)»erators  broiight  n|»  to  work  on  short  land  lines  are  inclined 
to  use  a  nervous,  light,  and  jerky  style.  This  when  ai)plied  to  cable  worldng 
causes  nnich  trouble.  The  dots  come  very  weak  or  fail  altogether,  while  the 
dashes  stick,  making  it  extremely  difficult  to  adjhst.  At  times  it  would  seem 
as  if  the  line  or  battery  were  giving  ti'ouble,  while  in  reality  the  fault  is  in  the 
sending. 


(450) 


r 
r 


Long  Submarine  Cables,  Telegraphy,  and  Tests. — Chapter  II.  15 

Ttie  cable  operator  needs  a  swinging,  .solid  style,  with  not  a  very  great  differ- 
ence between  the  dots  and  dashes,  but  with  a  uniform  contact.  With  such  style 
no  (llfTiculty  will  be  experienceil  in  keeping  the  relay  adjusted.  The  greater 
static  capacity  of  a  cable  the  greater  the  otTect  of  irreguhirities  in  sending. 

The  time  of  charge  of  a  cal>le  should  always  be  taken  into  cousidei-ation,  and 
the  sending  regulated  accordingly. 

ItEPEATEK.S. 

Wherever  possible  repeaters  sliould  be  inserted  between  a  land  line  and  a 
cable  instead  of  working  directly  through,  as  the  battery  is  increased  on  land 
lines  from  time  to  time  through  various  cau.ses,  such  as  weather  conditions,  bad 
joints,  and  connections,  etc.  By  the  insertion  of  repeaters  the  amount  of 
battery  going  into  the  cable  is  always  the  same,  and  the  adjustments  of  the 
instruments  on  the  cable  side  will  vary  but  little,  if  any.  The  operator  at  the 
repeater  station  should  keep  his  instruments  well  adjusted  to  the  conditions  of 
the  line,  making  the  relay  work  the  repeater  heavy  or  light  according  to  the 
requirements.  Very  often  the  signals  seem  clear  to  him,  but  do  not  reach  the 
other  station  properly.  The  trouble  will  probably  be  due  to  (iii-ty  contacts  in 
the  repeater.  Dust  accumulating  at  the  contact  points  of  the  sending  key,  or 
at  the  contact  points  of  the  reijeater.  is  a  common  cause  of  high  resistance  in  a 
circuit.  These  points  should  always  be  cleaned  with  crocus  cloth,  or  if  very 
dirty  or  corroded  with  a  very  fine  tile. 

GENERAL    NOTES. 

If  a  jar,  or  rattle,  is  noticed  on  the  receiving  relay  it  will  generally  be  caused 
by  a  loo.se  connection  somewhere,  unless  there  is  a  land  line  in  circuit  that  is 
swinging  against  something. 

Bef<ire  increasing  the  amount  of  battery  on  any  cable,  the  chief  operators  at 
each  end  should  consult  and  try  to  get  at  the  exact  cause  of  the  trouble  and 
report  immediately  to  the  officer  in  charge.  The  minimum  number  of  cells  of 
main-line  battery  which  will  operate  a  cable  efficiently  will  be  determined. 
After  the  numbcn-  is  determined,  all  operators  are  forl)idden  to  increase  the 
number  of  cells  except  by  authority  of  the  chief  operator,  who  will  report  the 
matter  to  the  officer  in  charge,  so  that  innnediate  steps  may  be  taken  to  remove 
the  cause  of  the  trouble. 

A  good  operator  will  always  know  by  the  "feel"  of  his  relay  the  condition 
of  the  circuit.  If  the  circuit  is  grounded  between  stations  his  home  relay  will 
work  stronger  than  usual ;  the  nearer  the  ground  is  to  his  end  the  stronger  the 
relay  will  work.  If  the  line  is  open  at  the  distant  end,  and  an  ordinary  relay 
is  used,  he  will  get  two  inductive  kicks  from  the  "  static  "  of  the  cable,  one  on 
closing  the  key  and  one  on  opening  it.  These  kicks  will  be  lighter  the  nearer 
the  disconnection  is  to  his  station,  as  there  will  be  less  "  static."  If  he  gets 
no  kick  the  disconnection  nuist  be  near  home.  With  a  polarized  relay  he 
will  get  the  click  on  his  relay  only  when  closing  his  circuit.  It  should  be  the 
duty  of  every  operator  to  get  familiar  with  this  "  feeling "  of  his  line  by 
getting  the  operator  at  the  other  end  to  free  the  line  for  a  few  minutes  and 
then  ground  it  direct  without  the  distant  relay  being  in  circuit  for  a  few 
minutes ;  he  can  then  put  his  home  relay  at  a  certain  adjustment,  which  he  can 
use  for  these  tests,  and  note  the  effect  with  the  distant  end  open  and  distant 
end  grounded  without  the  distant  relay  being  in  circuit  and  also  with  the  dis- 
tant relay  in  circuit,  as  it  is  normally. 

(451) 


16  Signal  Corps  Manual  No.  3. — Chapter  11. 

Whenever  a  lightning  arrester  is  used,  it  should  be  frequently  examined  for 
a  "  gi'ound  "  or  loose  connection.  A  piece  of  paper  moved  back  and  forth 
between  the  ground  plate  and  the  line  connection  will  generally  remove  any 
dust  or  foreign  substances  which  may  have  accumulated  there. 

In  a  plug  switchboartl  care  should  be  taken  that  the  plugs  are  clean  and  fit 
snugly  in  the  holes.  The  holes  should  be  cleaned  out  frecpiently,  as  in  certain 
climates  insects  find  it  convenient  to  nest  thei'ein.  Sometimes  the  holes  and 
plugs  become  corroded  or  worn  irregularly,  with  the  result  that  the  circuit 
becomes  partially  oi*  totally  disconnected.  If  a  trouble  like  this  occurs  it 
would  be  well  to  bridge  across  with  a  small  piece  of  wire  the  connections  made 
by  the  plugs. 

In  moving  offices  from  one  building  to  another  in  isolated  places  the  wiring 
is  often  crude  and  in  time  causes  trouble,  and  new  men  make  changes  from 
time  to  time  to  meet  the  emergencies  that  may  arise.  The  operator  in  charge 
should  make  a  diagram  of  the  office  connections,  .showing  the  location  of  each 
wire  and  post  it  in  a  prominent  place  in  the  oflice  and,  when  relieved,  explain 
it  all  in  detail  to  his  successor. 

The  electrical  engineer  or  a  thoroughly  competent  man  should  visit  all 
stations  from  time  to  time  and  remedy  any  deficiencies  in  the  conditions. 
Instruments  should  be  overhauled  and  properly  adjusted,  and  batteries  and 
wiring  gone  over  thoroughly. 

OPERATION   OF   LONG    SUBMARINE  CABLES. 

As  previously  stated  in  this  chapter,  Morse  apparatus  is  at  a  serious  dis- 
advantage on  cables  over  approximately  200  miles  in  length,  due  to  retardation 
of  signals  occasioned  l)y  large  electrostatic  capacity  of  such  cables,  and  the 
siphon  recorder,  a  more  delicate  form  of  receiving  apparatus,  is  almost  mii- 
versally  used  in  such  instances. 

What  has  been  stated  relative  to  wiring  at  cable  stations  where  Morse 
apparatus  is  used  applies  also  to  stations  where  tlie  siphon  recorder  is  in- 
stalled, and  great  care  should  be  tiikeii  to  obtain  a  high  insulation  of  all 
wiring  and  between  all   app:ii-atus  and  ciuiii. 

SIPHON    KICCOKUEKS. 

The  siphon  recorder  may  be  brielly  described  as  a  moving  coil  galvanometer, 
with  a  delicate  glass  siphon  attached  to  the  coil  in  such  a  way  that  the  mo- 
tions of  the  coil  are  ti'ansmitted,  very  nuich  magnified,  to  the  point  of  the 
siphon.  One  end  of  this  si])lion  dips  into  a  small  ink  well,  the  other  end, 
where  the  motion  is  greatest,  touching  the  moving  paper  tai)e.  This  tape  is 
kept  moving  steadily  by  means  of  a  small  electric,  .spring,  or  weight-driven 
motor.  Every  motion  of  the  coil  is  i-ecorded  as  a  deviation  in  the  straight 
line  being  drawn  on  the  tape,  :ind  signals  produced  by  sending  quick  impulst's 
from  either  the  posilive  or  negative  side  of  the  battery  will  be  recorded  as 
short  waves  above  or  lidow  I  his  straight  line.  To  render  the  siphon  more 
sensitive  by  reducing  its  friction  agiiinsi  llic  tape,  it  is  kept  in  constant  and 
rajiid  vibration  by  electromagnetic  means. 

The  construction  of  the  recorder  is  shown  in  (igures  11-f>  and  11-11. 

Figure  11-10  shows  a  simplilied  diagram  of  I  lie  coiniections. 

Figure  11-J»  is  the  large  sii)lion  recorder  used  generally  oii  (lie  long  cables. 
In  the  held  of  the  |>ermanenl  magnet  I!  the  Hat  rectangular  coil  .1  of  line 
insidiited  wire  is  susjieiided  by  tine  threads  above  and  below.  Fine  wires 
eonnecl    llie  recoi'dei-  cdil    with    llie  cable  circuil. 

(4.M') 


Lcr.g  Submarine  Cables,  Telegraphy,  and  Tests. — Chapter   I  1 


17 


AMicri  riirrctii  iiii|iiilscs  ;in-i\c,  tlicy  (Icllccl  tlic  cnil.  (lie  (lirt'clioii  (l('[icinlin« 
iiIiDii  llit>  poliirit.v  <>r  tlic  rccciviiiji  iiiiinilsc.  'I'licsc  motions  iirc  yononilly  very 
small.  Tlu'  coil  i.s  aKMclicil  l)y  two  line  sill<  tin-eads  to  a  sinjill  piece  of  alunii- 
nnni.  to  which  is  attached  I  lie  ;,'lass  .sii)hon  ('.  The  aluminum  piece  Is  itself 
susiiended  liy  a  tine  lioiizoiiial  wire.  The  .silk  threads  from  the  coil  being 
near  the  point  of  suspension  of  tlie  siplion,  every  motion  of  the  coil  and 
tln-eads  is  thus  maj^nitied  at  the  lower  end  of  the  siphon.  The  .siphon  dips 
at  the  upper  end  into  the  ink  well  I)  a;id  at  its  lower  end  lijjhtly  touches  the 
niovinj,'  tape  /•>'.  This  tape  is  moved  forward  steadily  by  the  gear  wheels  ./, 
which  are  driv(>n  l»y  a  shaft  extending  hack  and  carrying  a  indley  which 
is  driven  by    the   nictni-   //    through   a   tiexiltle  bell. 


F.g.  11-9.— LONG   SUBIVIARINE  CABLES,    LARGE  SIPHON    RECORDER. 


(453) 


18 


Signal  Corps  Manual  No.  3. — Chapter  11. 


To  eliminate  friction  of  tlie  siphon  on  the  paper  tape,  the  siphon  is  kept  in 
vibration  hy  means  of  a  small  electromagnet  /•'.  to  the  armature  of  which  is 
attached  the  horizontal  wire  carrying  the  piece  of  aluminum  and  the  siphon. 
Through  the  electromagnet  F  rapid  pulsations  are  sent  from  the  interrupter  G, 
which  is  similar  to  a  small  vibrating  bell  mechanism. 


V.liat.r    Cor.httt.onS 


THE    APPARATUS  MAY  BE  IDENTIFIED 
BY   MEANS  OF  LETTERS   HEREON  AND 
REFERENCE   TO     FiG^  ll-9. 


Fig.  11-10.— LONG    SUBMARINE    CABLES,    LARGE   SIPHON    RECORDER,    CONNECTIONS. 

The  interrupter  and  vibrator  are  controlled  l)y  a  small  rheostat  L  being 
included  in  their  circuit.  The  speed  of  the  motor  is  regulated  by  a  rheostat  A". 
On  the  other  side  of  the  recorder  is  an  adjustable  shunt  coil  which  regulates 
the  proportion  of  current  through  the  coil  .1,  coming  from  the  cable. 

The  small  recorder  (tig.  11-11)  is  u.sed  on  the  shorter  cables.  It  is  only  about 
one-fourth  as  sensitive  as  the  large  one  .lust  described.  In  its  essential  parts  it 
is  very  similar  to  the  lai"ge  <tne.  tin*  si])hon  suspension  lu'ing  somewhat  simjtler 
and  more  compactly  arranged. 

Tbe  permanent  magnets  of  both  these  recorders  have  coils  wound  around 
them  foi'  the  ])\n'i»ose  of  strengthening  their  magnetism,  in  case  it  is  weakened, 
by  sending  a  imnncnlary  direct  ciu'reiit  d'om  some  KHI-volt  source  through 
tliciii.  <'ar<'  iiiusi  lie  I  liken  llial  llie  current  is  direct  (not.  jdternating)  and 
that    il    is  sciil    in  llic  proper  direclion. 

Tlie  (iilhiw  ing,  iin  adjusi  nieiil  of  I  he  recorder,  the  vibra(<u',  and  motor,  is 
(li-iiwii  ill  pari  li-Mui  I'.eginners'  iMainiai  of  Submarim>  (^able  Testing  and 
\\  Diking,  by  <!.  M.  I'.aines: 


(454) 


Long  Submarine  Cables,  Telegraphy,  and  Tests. — Chapter  11.  19 


Fig.  11-11.— LONG    SUBMARINE    CABLES,    SMALL    SIPHON    RECORDER. 

AliJCSTMENT    OF    RECORDEK. 

The  present  form  of  recorder,  known  as  the  "  Hylirid,"  is  of  the  permanent 
magnet  type.  As  it  has  heen  found,  however,  that  the  magnets  lo.se  a  propor- 
tion of  their  strength  in  tropical  climates,  a  winding  of  insulated  copper  wire, 
with  a  resistance  of  about  8  ohms,  has  been  provided  for  them.  This  arrange- 
ment, whence  the  instrument  derives  its  name,  permits  of  the  restoration  of 
the  magnetic  field  strength  when  it  falls  below  its  normal  value. 

On  the  supposition,  then,  that  the  magnetometer  proves  the  magnetic  field  to 
have  fallen  below  10  Cuff  units,  a  current  from  an  E.  M.  F.  of  100  volts  should 
he  applied  to  the  aforementioned  coils.  For  this  purpose  the  ends  of  the  coils 
have  been  conveniently  brought  to  terminals  on  the  instrument  which  are 
marked,  respectively,  with  the  positive  and  negative  signs. 

The  operation  of  strengthening  the  magnetic  field  is  carried  out  in  the  fol- 
lowing manner : 

The  positive  pole  of  the  battery — iireferably  secondary  cells  or  dynamo, 
l)ecause  for  the  desired  effect  a  large  momentary  current  is  required,  therefore 
the  internal  resistance  nuist  be  inconsideraijle — is  connected  to  the  terminal 
marked  +.  To  the  other  terminal  should  be  joined  a  short,  thick  wire.  The 
current  is  applied  by  three  or  four  momentary  contacts  between  this  wire 
and  the  negative  pole  of  the  battery  or  dynamo,  due  care  being  observed  that 
tile  operator  does  not  include  himself  in  the  circuit. 

The  "  Hybrid  "  may  also  be  used  as  an  electromagnet  recorder  by  maintaining 
a  battery  on  the  magnet  coils.  It  is  intended,  however,  that  it  should  be  em- 
ployed as  a  permanent  magnet  instrument,  its  field  strength  being  kept  at  its 
normal  value  in  the  manner  indicated. 


(455) 


20  Signal  Corps  Manual  No.  3.— Chapter  1 1, 

The  double  liber  between  the  signnlinj;  et)il  ami  the  siphon  cradle  is  an  im- 
provement upon  the  old  single-tiber  attachment.  By  this  new  arrangement  the 
full  movement  of  the  coil  is  imparted  to  the  siphon. 

The  renewal  of  the  double  tiber,  when  necessary,  is  effected  in  the  following 
manner : 

1.  Set  the  coil  square  and  tix  it. 

2.  Place  the  bridge  piece  in  its  central  position. 

3.  Turn  the  milled  head  at  the  right-hand  extremity  of  the  bridge  until  the 
siphon  cradle  hangs  perpendicularly. 

4.  Attach  one  end  of  the  fiber  to  the  right  side  of  the  top  of  the  coil ;  fix  it 
with  the  shellac  supplied  for  the  purpose ;  pass  it  round,  or  through,  the  siphon 
cradle;  fix  it  there  and  lead  it  back  to  the  top  of  the  left  side  of  the  coil, 
where  it  will  also  be  secured. 

Great  importance  is  attached  to  the  preservation  of  the  following  equidis- 
tances : 

1.  Between  the  attachment  of  the  fiber  ends  and  the  coil  center. 

2.  The  two  points  where  the  fiber  passes  through  the  siphon  cradle  and  the 
cradle  wire. 

To  obtain  the  most  suitable  adjustment  of  the  fibers,  fir.st  slacken  them  and 
set  the  siphon  in  an  upright  position  by  turning  the  milled  head  which  holds  the 
cradle  wire.  Next,  tighten  the  coil  fillers,  and  if  the  siphon  be  defiected  from 
the  perpendicular  bring  it  back  by  a  slight  turn  of  the  nulled  head  carrying  the 
coil  suspension.  This  will  square  the  coil  and  bring  back  the  siphon  to  the  per- 
pendicular at  the  same  time. 

If.  on  again  tightening  the  coil  fil)ers,  the  siphon  deviates,  it  will  be  found 
that  the  aforementioned  equidistances  have  not  been  preserved. 

A  broken  coil  suspension  admits  of  easy  repair. 

Thread  a  piece  of  silk  through  the  aluminum  attachment  at  the  top  of  the 
coil,  tie  the  ends  in  a  loop,  and  pass  them  up  through  the  coil  cap  over  the  small 
pulley  above  it. 

A  proper  adjustment  of  the  signal  c(»il  is  a  matter  of  utmost  importance  for 
securing  the  double  result  of  maximum  signal  speefl  and  definition.  Experiment 
has  demonstrated  that  for  rapid  speeds  better  defined  signals  are  obtained  by 
discarding  the  shunt  and  tightening  the  coil  suspension.  By  this  means  a 
quicker  periodic  movement  is  given  to  the  coil.  The  shunt  exercises  a  damping 
('ffect  on  the  coil,  rounding  the  signals  in  such  a  manner  as  to  render  them 
unreadable  at  high  .speeds. 

This  ju'i-iodic  movement  of  the  C(til  would  also  re(iuire  attention  if.  lor  in- 
stance, it  were  (ouiid  neces.sary  to  change  over  an  electrically  long  cable  to  an 
instrument  adjusted  for  a  short  one,  or  vice  versa.  Vov  the  long  cable,  with 
a  slower  signaling  speed,  a  larger  periodic  movement  of  the  coil  would  be 
r('(|uire(I  to  give  a  sufhcient  ami)litn(I('  lo  I  lie  signals. 

With  r<'gard  lo  Hie  adjusliiicnt  ot  the  vibrator,  the  screw  and  weight  on  the 
interrupter  (1,  figure  11-12,  is  the  most  important  factor,  and  should  claim  tirst 
attention  if  a  failure  of  ink  occur.  For  the  vibration  of  a  long,  fine  siphon  the 
weight  will  need  a  higher  position  on  the  make-and-break  j-od  than  would  b(> 
required  for  a  coarse  tube.  The  movement  of  the  vibrator  armature  should  b«' 
so  regidated  as  to  be  nearly  invisible.  Variation  in  the  thickness  of  the  ink  fiow 
may  often  be  obtained  by  altering  the  rheostat  resistance  L. 


(4r.(i) 


Long  Submarine  Cables,  Telegraphy,  and  Tests. — Chapter  11.  21 

MUIUUEAD'.S     VlBKATOIl. 

Figure  11-12  explains  the  connections  of  tliis  apparatus.  A  battery  of  from 
3  to  5  volts,  with  low  inti'rnal  resistance,  is  rciiiiiriMl  to  jtroperly  operate  it. 
Four  Edison  primary  cells,  tyjie  V  or  their  ('([uivalent.  will  suflice.  Uesistanct; 
L  permits  the  retrulation  of  the  current  as  desired.  The  action  and  use  of  the 
instrument  are  too  weU  known  to  need  a  lenythy  descriiition.     It  will  he  found 


mmom 


'^   -^ 


Fig.  11-12.— LONG    SUBMARINE   CABLES,    SIPHON    RECORDER,    MUIRHEAD    VIBRATOR. 

CIRCUITS. 


that  the  best  result  is  obtained  when  the  interrupter  (1  works  almost  silently. 
Fine  siphons  are  also  recommended  as  bein^  susceptible  of  greater  vibration 
than  coarse  ones,  with  a  consequent  reduction  of  friction  between  the  siphon 
point  and  the  paper.  The  spark  coil  connected  between  the  make-and-break 
contacts  is  indicated  as  J/  in  the  plan  below.  The  resistances  of  the  interrupter 
G  and  vibrator  F  coils  are  about  10  ohms  per  pair. 

THE     MOTOR. 

The  present  form  of  recorder  motor  is  a  development  of  the  orig:inal  type  intro- 
duced by  Lord  Kelvin.  A  cam  is  suitably  adjusted  to  allow  the  current  from  the 
driving  battery  to  pass  at  the  proper  points,  in  sequence,  through  the  coils  of 
the  fixed  electromagnet  below  the  revolving  drum.  A  set  of  resistances  K,  figure 
11-9,  on  the  motor  base  can  be  introduced  into  the  circuit  of  the  battery  and  the 
electromagnet  coils  for  the  regulation  of  the  speed. 


(457) 


9-2 


Signal  Corps  Mcinual  No.  3. — Chapter  11. 


Soft-iron  bars,  disposed  :u  equal  distances  from  each  otlier,  are  fixed  longi- 
tudinally on  the  surface  of  the  rotating  brass  cylinder,  through  the  center  of 
which  passes  the  axle  upon  which  the  whole  revolves. 

At  the  instant  a  bar.  attracted  by  the  electromagnet,  arrives  opposite  the  core 
of  the  latter  the  battery  is  cut  off  by  the  cam.  The  momentum  carries  the  bar 
past  and  brings  the  next  near  the  core  of  the  electromagnet.  The  cam  again 
closes  the  current,  giving  another  impulse  to  the  drum,  and  so  on.  The  result 
of  this  series  of  operations  is  a  continuous  revolution  of  the  drum. 

For  operating  the  recorder  motor  a  battery  of  from  6  to  12  volts  with  low  in- 
ternal resistance  and  a  large  ampere-hour  output  is  required.  Six  to  twelve  Edi- 
son primary  type  V  cells  or  their  equivalent  will  prove  satisfactory. 

OrER.iTION    OF    MOTOR    BY    ELECTRIC-LIGHT    CURRENT. 

Where  the  office  is  provided  with  electric  lights  fed  by  direct  current  from 
110-volt  circuits  the  table-lamp  circuit  can  be  utilized  in  place  of  a  battery,  as 
shown  in  figure  11-13  for  operating  the  motor. 


Fig.  11-13.— LONG    SUBMARINE    CABLES,    SIPHON    RECORDER.    TO    OPERATE    MOTOR 
FROM     ELECTRIC     LIGHTING    CIRCUIT.    • 

The  8-ohm  resistance  coil,  made  up  of  sufficiently  large  wire  not  to  heat  witli 
]  ampere,  is  in  circuit  with  the  32-candlepower  table  lamp.  This  coil  is  shunted 
by  wires  from  the  motor,  as  shown.  An  E.  M.  F.  of  approximately  8  is  obtained 
at  the  motor  terminals  by  this  arrangement. 


-120  vol  Is-* 


2-32  0.P  Lamp3^C\      i\ 
65ohm5W       V 


E^lectric  Ughf-hsads 


Marble  slab, 
/6"x^"x.  7" 


Nol7  Oerrnan 
silver  vans 


^*~fusGs:^Amp. 


Fig.  11-14.- 


-LONG    SUBMARINE   CABLES,    CURRENT    SUPPLY    AT    SEATTLE   TERMINUS 
OF    SEATTLE-SITKA    CABLE. 


(458) 


Long  Submarine  Cables,  Telegraphy,  and  Tests. — Chapter  II.  23 

Figure  11-14  .shows  another  method.  The  latter  is  now  being  used  in  the 
Signal  Corps  cable  othoe  at  Seattle,  and  res^ults  are  entirely  satisfactory.  The 
coil  may  be  extended  to  supply  additional  instruments,  such  as  cable  trans- 
mitters, with  current. 

The  motor  and  vibrator  should  not  be  driven  by  the  same  battery  on  account 
of  the  constant  variation  in  the  potential  of  the  latter.  Say  the  motor  battery 
has  an.E.  M.  F.  of  4  volts  and  an  internal  resistance  of  1  ohm.  The  motor  coils 
have,  also,  a  resistance  of  about  1  ohm  each.  The  potential,  therefore,  outside 
the  battery  constantly  varies,  by  the  make-and-hreak,  between  '2  and  4  volts. 
This  variation  would  disturb  the  regularity  of  the  vibrations. 

fAUK  OF  RECORDER  SIPHONS,  INK,  ETC. 

Recorder  fiipJtons. — The  punk  furnished  with  tool  boxes  makes  the  best  mate- 
rial ft)r  bending  siphons.  A  lighted  paper  spill  made  of  recorder  tape  is  also 
a  handy  means  of  bending  siphon  tulies.  A  small  spirit  lamp  is  berter.  Tilt 
the  lamp  forward  ;  the  tubes  must  not  be  thrust  into  flame ;  a  slight  contact  with 
the  blue  flame  underneath  will  bend  the  tubes  without  melting  and  closing  the 
tube.    By  using  a  spirit  lamp  both  hands  are  available. 

The  best  way  of  breaking  off  the  surplus  tube  is  by  pressing  it  betSveen  the 
thumb  nail  and  the  forefinger.  This  usually  leaves  a  clean,  level  break,  requir- 
ing a  very  little  grinding.  A  medium  fine  carborundum  stone  or  a  fine  emery 
sti^^'k  may  be  used  to  smooth  the  siphon  point.  Another  method  is  by  means  of 
the  miniature  battery  motor  fitted  with  a  small  emery  wheel. 

Recorder  ink  is  made  by  dissolving  some  of  the  more  soluble  aniline  dyes  in 
water,  to  which  is  added  alcohol.  In  general,  about  one-fifth  alcohol  is  correct, 
but  the  amount  of  alcohol  depends  upon  the  quality  of  the  tape  and  dryness  of 
the  air.  "  Soluble-blue "  aniline  is  good,  and  some  of  the  "  Diamond  dyes " 
make  good  ink.  It  is  best  to  use  boiled  water.  After  the  aniline  is  thoroughly 
dissolved  the  ink  should  be  run  through  a  filtering  paper.  The  bottle  should  be 
kept  corked  and  care  taken  to  exclude  dust  and  lint  from  the  ink  well. 

If  siphon  gets  choked,  heat  the  was  soldering  strip  used  for  putting  siphons 
on  and  gently  rub  along  siphon.  This  will  force  the  ink  out  and  remove  the 
obstruction. 

\\hen  recorders  are  not  in  \ise  for  some  time  the  siphons  should  be  inunersed 
in  water  instead  of  ink.  Empty  ink  well,  fill  with  water,  letting  paper  tape  run 
till  all  ink  is  drawn  out.  Bettor  still  is  the  use  of  alcohol  instead  of  water. 
When  ink  is  drawn  out  of  siphons,  the  alcohol  filling  tube,  the  alcohol  can  be 
returned  to  bottle  and  siphon  left  dry.  On  starting  recorder  again  the  ink  will 
flow  freely  without  assistance;  the  alcohol  having  evaporated  leaves  tube  dry. 

Ground  connections. — In  no  case  should  the  recorders  be  connected  with  the 
same  ground  as  land  lines  or  even  to  the  same  cable  sheath  that  connect  to 
instnnnents  where  Morse  is  used.  Owing  to  the  great  delicacy  of  the  recorder, 
this  will  cause  the  Morse  working  to  disturb  the  recorder  signals.  (See  remark.s 
pertaining  to  ground  connections  appearing  later  in  this  chapter.) 

AUXILIARY   APPARATUS   FOR   SIPHOX   RECORDER   WORKING. 

Double  keys  are  used  similar  to,  those  shown  in  figure  11-15.  The  battery 
binding  posts  are  on  the  sides,  while  the  earth  and  line  posts  are  at  the  back. 
Connections  and  switch  used  are  shown  in  figure  11-15. 

The  signaling  condensers  may  be  either  in  the  transmitting  circuit,  in  the  re- 
ceiving circuit,  or  both.     In  the  Alaskan  cable  offices  the  condenser  is  inserted 

46581°— 17 30  (459) 


24 


Signal  Corps  Manual  No.  3. — Chapter  1  1 


in  the  receiving  circuit  only  as  sliown  in  figures  11-15,  11-16.  and  11-17.  These 
condensers  should  be  very  solidly  made  and  having  ample  thickness  of  dielectric 
to  prevent  short-circuiting  by  puncturing  or  rough  handling. 


Hlljlllllllllllllp 

Battery 


Fig.  11-15.— LONG    SUBMARINE    CABLES,    SIPHON    RECORDER    SET,    SIMPLIFIED    CON- 
NECTIONS. 

At  the  offices  on  the  longer  cables  is  provided  a  large  coil  forming  an  induc- 
tance shunt  to  the  cable.  (Figs.  11-16  and  11-17.)  This  coil  has  resistance  in 
series  with  it  mounted  in  the  same  case  with  the  condenser  shunt. 

The  battery  required  to  operate  long  cables  with  siphon  recorder  is  small 
when  compared  with  the  operation  of  land  lines.  For  example,  the  Seattle- 
Sitka  cable,  1,085  miles,  is  operated  with  10  ordinary  dry  cells;  the  A'aldez- 
Sitka  cable,  approximately  600  miles,  with  2  dry  cells;  the  Juneau-Sitka  cable, 
approximately  300  miles,  with  1  dry  cell.  During  extreme  low  insulation  the 
Seattle-Sitka  cable  has  been  operated  when  less  tlinn  one-tenfli  of  one  mili- 
arapere  came  through  from  the  di.stant  end.  The  trallic  on  tii(>  Seattie-Sitka 
cable  is  practically  continuous  for  15  or  more  hours  each  day,  and  it  has  been 
found  that  dry  cells  are  entirely  satisfactory.  The  dry  cells  for  this  service  lasi 
from  six  to  eight  months.  The  condition  of  these  cells  should  be  frequently 
ascertained. 

.\RR.\.N(iKMENT    OK    IXSTRUMKNTS    lOK    OI'KK.VTINC    r.ONC    CAHLES. 

.\s  siphon  recorders  iire  now  alniosl  niiiv<>rsally  usimI  on  long  cables,  office 
.sols  of  this  kiiwl  only  will  he  (Icscrihed.  Th(»  siini>l(^st  arrangement  of  the 
siphon  recorder  set  is  shown  in  tignrc  11-15.  With  the  switch  in  sending  ])osi- 
tion  it  is  seen  that  the  negative  end  of  battery  is  ])ul  to  line  wIkmi  the  left  Icey 
lever  (dot)  is  depressed,  and  the  positive  when  the  i-iglit    (dash)    is  depressed. 


IGO) 


Long  Submarine  Cables,  Telegraphy,  and  Tests. — Chapter  1  I . 


25 


I 


Witli  swifcli  set  ;it  rcceiviii};.  the  iiu-oiiiiiif;  currents  pass  tliroufih  condenser 
and  ret-order  to  earth.  <  >n  the  longer  cables  Muirhead's  arrangement  of  the 
circuit  is  shown  in  figure  31-16. 


Cable 


/ 


Switch 
Senoing    ^     ^Receivimj 


M-ey 


H       Q 


'h|i|i|i|i|i|i|i|i|--' 

Battery 


I 


Condenser 


Seconder 


Fig.  11-16.— LONG  SUBMARINE  CABLES,   SIPHON    RECORDER,    MUIRHEAD'S  ARRANGE- 
MENT   OF    CIRCUIT. 


SWITCH 

To  lef-t-Sendinq  po^hon 
To  right-  Rxei  ving    « 


Fig.  11-17. 


-LONG    SUBMARINE   CABLES,    ACTUAL   CONNECTIONS   AT    ALASKAN    CABLE 
OFFICES. 


In  the  receiving  circuit  the  inconiing  currents  are  first  partly  shunteil  to 
earth  through  the  adjustable  resistance  and  inductive  resistance  coil.  This, 
while  reducing  the  signals  somewhat  in  amplitude,  tends  to  make  them  squarer 
and  more  sharply  defined.  The  unshunted  portion  of  currents  then  pass  on, 
part  of  them  going  directly  to  recorder  and  earth  through  the  condenser  shunt 


(461) 


26 


Signal  Corps  Manual  No.  3. — Chapter  II. 


adjustable  resistance,  and  the  other  through  the  condenser  and  recorder.  By 
adjusting  the  resistances  and  condenser  the  signals  can  be  leveled  off  to  the 
most  legible  shape. 

The  actual  circuit  arrangement  just  described  is  shown  in  figure  11-17. 

The  inductance  coil  shown  in  diagrams  is  not  used  on  short  cables  lilje 
Valdez-Seward-Cordova  cables,  about  264  statute  miles. 

Figure  11-18  is  a  diagram  of  circuits  of  a  duplex  and  simplex  system. 


gmsmrfT^V  I'ailt  ^.'P^ 


AMERICAN  TELG.  MAVER,ie99  EOlTION.r  277 


Fig.  11-18.— LONG   SUBMARINE  CABLES,   SIPHON    RECORDER,    DUPLEX    AND   SIMPLEX 

SYSTEMS,    CONNECTIONS. 

AUTOMATIC    TKANSMITTEKS. 

WIkm'c  Mie  traflic  is  lic^avy  enougli  lo  warrani  tlic  expense  of  installation  the 
auloinatic  transmitter  sliouhl  be  u.sed.  The  maximum  signaling  speed  of  the 
caliie  may  thus  be  maintained;  the  signals  are  uniform,  and,  in  the  words 
of  a  superintendent  of  a  conmiercial  cable  company,  "it  does  not  stop  to  talk." 
'I'lic  Cuttriss  aut<»matic  transmitter,  hereafter  described,  lias  proved  very  sat- 
isfactory on  th<>  Seatt]e-Sitl<a  cal)le. 

The  apparatus  uses  a  iierl'orated  tape  automatically  f<'(l  througli  liic  instru- 
ment liy  means  of  a  smalPeh'ctric  motor.  The  perforations  are  previously 
made  on  a  machine  similar  to  a  typewriter  and  by  means  of  them  the  dot- 
and-dash  cliaracHTs  arc  li-anslVrrcd  electrically   to  the  caljle  conductor. 

TMK    (TTTRISS    ATTOMATK'    TRANSMITTKU. 

'i'lic  uii-jiig  of  the  Cuttriss  automatic  transmitter,  figure  11-10,  illustrates 
I  lie  method  of  operation  of  the  instrumcMit.  It  is  the  i)i'actice  to  connect,  as 
auxiliary,  transmitters  of  the  ordinary  telegraph  type  with  the  Cuttriss  trans- 
mitter. The  drive  of  tlie  Cuttriss  transmitter  is  a  motor  with  permanent 
field  magnets.  The  speed  is  governed  by  a  make-and-break  contact,  which  is 
adjusted  by  a  knurled  screw  jtrotruding  through  the  end  of  the  instrument 
case.  The  more  continuous  the  "  make,"  or,  in  other  words,  the  closer  the 
adjustment  of  governor  contacts,  the  faster  should  be  the  speed.     Each  revo- 


(4GJ) 


Long  Submarine  Cables,  Telegraphy,  and  Tests. — Chapter   II.  27 

lutlon  of  the  armature  .shaft  of  motor  turns  the  star  wheel  one-tentli  of  an 
iiu-ti.  The  outside  star  wlieel  contains  two  sols  of  lioles  iiitn  which  the  pins 
of  liic  piclxers  fall  when  oi»posite  the  holes  in  Hit-  ta|ic.  The  outside  holes 
control  the  "dash"  inipui.ses.  Inside  the  case  is  a  master  contact  at  which 
the  make  and  break  of  the  local   circuits  are  made.     The  adjustment  should 


Fig.  11-19. 


-LONG  SUBMARINE  CABLES,  CUTTRISS  AUTOMATIC  TRANSMITTERS,  CON- 
NECTIONS. 


be  such  that  the  picker  contacts  are  closed  before  the  make  is  made  on  the 
master  contact ;  also  the  picker  contacts  should  be  opened  after  the  break 
of  the  master  contact.  Improi)er  adjustment  will  be  indicated  by  the  pickers 
sparking.  When  sent  out  the  instrument  is  carefully  adjusted,  but  shoidd 
later  adjustment  lie  necessary  the  following;  procedure  is  su.i^fiested : 

See  that  the  inside  steel  cam  is  fast  on  the  shaft.  Itevolve  the  armature 
shaft  until  the  slot  in  the  steel  cam  is  on  top.  At  this  point  the  pickers  should 
drop  exactly  in  the  center  of  the  holes  of  tlu>  outside  star  wheel.  The  pins 
of  the  two  star  wheels  should  always  be  exactly  opposite  each  other.  With 
the  slot  of  the  steel  cam  upward,  it  should  be  possible  to  revolve  the  armature 
shaft  a  portion  of  a  turn  without  moving  the  star-wheel  shaft.  The  screw  on 
the  master  contact  arm  should  then  he  adjusted  for  maximum  period  of  con- 
tact per  revolution.  As  the  armature  shaft  is  revolved  the  master  contact 
should  be  broken  just  before  the  star  wheel  beirins  to  move.  The  pickers 
should  have  very  small  play,  just  enoufrh  to  maintain  the  "  open  "  in  the 
circuit.  The  make  and  break  of  the  master  contact  should  be  properly  timed. 
This  is  adjusted  when  necessary  by  rotating  the  vulcanite  eccentric  cam  on 
the  armature  shaft  so  that  the  high  point  comes  at  the  proper  part  of  the 
cycle. 

"(46S) 


28  Signal  Corps  Manual  No.  3.— Chapter  11. 

TRANSXriTTER-TAPE    PERFORATORS. 

Tlic  iicrforitfor  iiKinufactnred  liy  the  Kleinsclunidt  Elet'tric  Co.,  New  York, 
li.-i.s  tlie  aiiiH'ariiiici'  ot  a  typewrilcr ;  the  (lei)rt'.s.sion  of  any  one  key  makes  all 
perforation  necessary  for  the  corresponding;  character.  It  is  usually  manu- 
factured to  operate  on  110-volt  direct  current,  but  can  be  manufactured  to 
operate  on  hijrher  or  lower  voltages. 

This  perforator  requires  no  special  skill  for  its  operation,  and  has  the 
ailvantaije  of  being  about  three  times  as  rapid  as  the  familiar  INIuirhead 
type.  One  extra  set  of  pimches  and  dies  should  be  kept  on  hand.  Specifica- 
tions for  maintaining,  cleaning,  and  adjusting  the  Kleinschniidt  perforator 
may  be  obtained  from  the  manufacturer. 

NOTES    ox    THE    EFFICIENT    WORKINC    OF    A    CAHLK    STATION    AND   ON    TROT'RLES    THAT 

OCCUR. 

See  that  the  batteries  are  kept  in  good  condition  and  well  insulated  from  each 
other  and  outside  damp  or  metallic  surfaces. 

All  office  leads  should  be  well  insulated.  It  is  better  not  to  bunch  them 
together  or  bend  sharply  at  an  angle.  Whenever  binding  posts  or  switches  are 
used  they  should  be  frequently  overhauled  and  cleaned.  A  high  resistance 
at  a  connection  is  a  very  common  source  of  trouble. 

Light,  snappy  sending  over  a  long  cable  will  produce  weak  and  distorted 
signals  at  the  distant  end.  All  contacts  should  be  uniformly  made  and  with  a 
cushiony  or  springy  style.  See  that  the  levers  of  key  spring  back  well 
against  the  back  contact,  which  becomes  a  part  of  the  line  circuit  when  the 
opposite  key  is  used.     This  contact  also  permits  the  cable  to  discharge  to  earth. 

The  amount  of  sending  and  receiving  condensers  to  be  used  can  best  be  regu- 
lated by  experiment,  the  resistance  and  capacity  of  the  cable  and  the  amount 
of  battery  used  being  the  chief  basis  to  .ludge  by  (from  20  to  GO  micTofarads 
gives  a  range  sufliclent  for  all  general  conditions).  Where  no  sending  con- 
densers are  used  it  is  well  to  interpose  an-  inductance  coil  between  the  line 
and  ground  parallel  with  the  receiving  condenser  and  recorder.  This  in- 
ductance coil  is  to  have  a  resistance  in  series  with  it  for  adjustment.  The  con- 
denser is  to  be  shuntetl  by  an  adjustal)le  resistance.  With  this  inductance  leak 
in  circuit  it  will  be  necessary  to  increase  the  sending  battery,  as  it  acts 
as  a  shunt  on  the  recorder.  With  a  ])ro])er  adjustment  of  the  resistance  in 
series  with  the  liidnctance  coil  and  of  the  resistance  shunting  the  condenser. 
tlie  signals  can  be  made  of  uniform  defiection  and  will  lose  that  irregular 
rising  and  railing  off  which  is  a  bad  featmv  in  long  cables. 

If  the  (lislanl  station  coinidaiiis  of  signals  being  small  or  \V(>ak  it  is  well  to 
lest  the  battei-y  for  voltage  at  the  cable  terminals,  and  if  the  voltage  shows 
normal  the  trouble  is  due  to  a  high  resistance  caused  either  by  bad  contact 
of  llie  key  or  other  bad  connections  in  the  circuit.  If  there  is  a  spare  set  in 
the  ollice.  switch  over  iind  ask  if  signals  are  any  better.  If  the  reply  is 
negative  the  trouble  must  be  in  some  coimections  which  nvv  coimnon  to  both 
sets,  which  can  be  seen  in  the  ollice  diagram  of  connections.  This  is  on  the 
assumption  that  there  is  no  trouble  at  the  other  station.  If  the  distant  station 
complains  of  key  failing  and  states  he  gets  no  "  dots  "  or  only  occasional  "  dots  " 
from  yon  the  lionhle  will  invariably  b(>  found  in  a  flirty  point  either  at  the 
front  contact  of  the  "dot  key"  or  the  IkicI:  cofitact  of  the  "dash  key."  If 
(lie  complaint  is  of  "  daslu'S  "  failing  the  positions  are  reversed — that  is,  at  the 


(4r,\) 


Long  Submarine  Cables,  Telegraphy,  and  Tests. — Chapter  11.  29 

front  contact  of  tlie  "  dasli  key"  ami  the  back  contact  of  the  "dot  key."  A 
li.ti;ht  touch  with  a  very  fino  file  will  clean  the  key  contacts.  The  receiving 
station  shouhl  overhaul  and  (itMii  his  connections  in  the  switch  and  see  that 
Ills  condenser  and  shunt  coinjections  and  contacts  are  all  right.  A  juniper 
or  hridge  of  a  small  i)iece  of  wire  can  be  put  across  the  different  connections 
in  the  switch  to  prove  that  tiie  contacts  are  all  right.  A  variable  resistance 
in  the  inductance  coil  circuit,  or  condenser  shunt  circuit,  or  a  faulty  condenser 
will  produce  variable  signals.  After  .seeing  that  the  connections  are  properly 
made  and  contacts  clean,  and  the  signals  still  varj'  from  large  round  signals 
to  small  shai'p  signals  and  at  times  come  normal,  the  condenser  should  be  tested 
for  insulation. 

A  faulty  condenser  will  give  the  above  effect.  In  case  communication  is  lost 
with  distant  station,  cut  out  switch  and  office  connections  and  run  wires  to  line 
and  earth  direct  where  they  enter  office  and  connect  up  as  in  diagram 
(fig.  11-15).  After  calling  for  a  sufficient  time  and  no  answer  received,  short- 
circuit  condenser  by  putting  a  wire  across  from  plate  "A"  to  plate  "  B  "  and  call 
again.     This  will  prove  if  trouble  is  local  or  otherwise. 

After  both  stations  have  overhauled  their  office  connections  and  the  trouble 
still  remains,  tests  should  be  made  of  the  main  cable  and  earth  cable.  In 
the  case  of  long  underground  cables  it  very  often  happens  that  joints  become 
corroded  and  eaten  away.  This  is  ijarticularly  the  case  where  there  are  electric 
railways  in  the  vicinity. 

By  keeping  the  field  magnets  adjusted  close  to  the  signal  coil  the  trouble  from 
small,  quick  extraneous  currents  will  be  very  much  lessened.  If  the  earth  cur- 
rents are  very  strong  the  shimt  on  the  receiving  condenser  should  be  greatly 
increased  or  set  to  infinity.  When  the  earth  currents  interfere  Avith  operation 
and  the  insulation  of  the  cable  will  permit,  the  sending  batteries  may  be 
increased. 

The  signals  can  be  regulated  by  the  recorder  shunt  to  the  required  size.  One 
of  the  principal  things  in  maintaining  good  signals  is  the  syphon  and  its  vibra- 
tiim.  The  point  of  the  syphon  should  be  uniformly  ground  and  bent  so  as  the 
l)est  flow  of  ink  is  obtainable.  If  the  nose  is  bent  too  abruptly  or  not  far 
enough  a  very  poor  line  is  the  result.  It  will  be  found  when  a  new  syphon  is 
put  on  that  perhaps  the  period  of  vibration  Is  different  from  what  it  was  for 
the  old  syphon.  It  will  then  be  necessary  to  adjust  the  interrupter  by  turning 
back  and  forth  and  sliding  the  weight  on  the  armature  lever  up  and  down  \mtil 
the  proper  period  is  obtained.  Also,  the  rheostat  in  the  battery  circuit  can  be 
changed  to  give  desired  effect.  If  the  syphon  is  not  properly  mounted  it  will 
be  ditticult  to  get  proper  vibration.  If  blots  of  ink  form  rapidly  on  the  nose  of 
the  syphon  it  is  better  to  change  it  and  substitute  one  better  ground.  By  heat- 
ing a  .small  iron  and  putting  a  little  wax  on  the  nose  of  syphon  a  rough  line  can 
be  improved.  Once  the  kind  of  syphon  that  gives  best  results  is  established  a 
dozen  or  so  similar  ones  properly  ground  should  be  made  ready  for  use  so  the 
one  can  be  readily  mounted  when  necessary.  Keep  the  bearings  of  the  motor 
well  oiled  and  the  battery  contact  maker  cleaned  and  free  from  sparking.  If 
the  contacts  are  too  close  and  an  arc  forms,  the  battery  will  be  run  down 
quickly  and   motor  run  irregularly. 

(iltOUNUS  FOR  SIBMAKINE  CABLES  IN  OR  NEAR  LARGE  CITIES. 

The  earth  in  large  cities  and  vicinity  is  charged  with  positive  electricity 
from  electric-car  lines  and  leakage  from  electric-light  circuits.  This  positively 
charged  earth  causes  currents  to  flow  into  the  surrounding  country  and  espe- 

(465) 


30  Signal  Corps  Manual  No.  3.— Chapter  11. 

cially  on  any  conductor  leading  away  from  the  cities,  such  as  the  armor  of  a 
submarine  cable  which  lands  in  the  cities. 

The  delicate  current  used  in  submarine  telegraphy  is  much  disturbed  by 
these  varying  earth  currents  when  the  ground  is  made  to  the  earth  or  cable 
armor  in  or  near  the  large  cities.  For  this  purpose  an  extra  cable  is  run  some 
distance  into  the  sea,  its  length  depending  on  the  amount  of  the  disturbance 
caused  by  the  above-mentioned  earth  charge. 

The  single  copper  conductor  of  this  earth  cable  should  not  be  grounded 
directly  to  the  armor  or  other  metallic  body  at  the  extremity  of  the  earth  cable, 
for  local  galvanic  action  will  occur  between  the  two  dissimilar  metals,  and 
trouble  from  this  cause  will  ensue.  The  copper  core  of  the  single-conductor 
ground  cable  should  be  spliced  to  an  iron  wire,  and  all  of  the  copper  core  and 
the  joint  carefully  insulated,  to  entirely  exclude  moisture,  and  this  iron  wire 
carefully  soldered  to  a  mass  of  iron  and  then  sunk  in  the  bottom  of  the  sea. 

A  better  method  is  to  use  a  two-conductor  cable  from  cable  landing  to  several 
miles  out  to  sea,  splicing  one  conductor  of  the  two-conductor  cable  to  the 
conductor  of  the  long  single-conductor  cable  and  grounding  the  other  conductor 
in  the  following  manner : 

To  connect  the  second  conductor  of  the  twin  core  to  the  sheathing  wires  of 
the  cable,  proceed  by  preparing  the  armor  wires  for  an  overlapping  splice  in 
the  usual  manner  for  joining  two.  single-core  cables,  except  that  on  the  end 
that  usually  has  all  the  wires  cut  off  at  the  splice  (the  single-conductor  cable 
in  this  instance)  five  or  six  of  the  armor  wires  are  made  7  or  S  inches  longer 
than  the  rest,  so  as  to  provide  a  convenient  surface  for  making  the  groiind  con- 
nection. On  the  other  cable  end  (two-conductor  cable)  the  armor  wires  will,  of 
course,  be  left  20  or  30  feet  long.  The  regular  cable  conductor  is  then  spliced  in 
the  same  manner  as  when  joining  single-conductor  cables  together.  After  this 
joint  is  completed  and  served  with  tape  or  spun  yarn,  mill  (wrap)  the  copper 
strands  of  the  extra  or  ground  conductor  around  the  five  or  six  armor  wires  that 
were  left  longer  for  that  purpose,  making  a  joint  4  or  5  inches  in  length,  which, 
if  possible,  should  be  carefully  wiped  with  solder.  Both  the  copper  and  iron 
wires  should  be  thoroughly  cleaned  before  the  joint  is  made,  and  these  joints 
thoroughly  insulated  with  i)ure  rubber  or  Kerite  tape,  applied  warm.  It  is 
highly  important  that  moisture  does  not  come  in  contact  with  the  joints  between 
the  copper  and  galvanized-steel  armor  wires.  After  serving  this  joint  and  the 
core  splice  with  tape  or  spun  yarn  as  a  bed  for  the  armor  wires,  you  have  a  con- 
dition that  does  not  differ  greatly  from  the  joint  of  a  two-conductor  cable,  the 
splice  being  completed  with  the  long  ends  of  armor  wires  and  served  in  the  ordi- 
nary manner. 

In  these  methods  there  are  no  dissimilar  metals  exi)os(>d  lo  the  wiiter  to 
cause  trouble. 

By  soldering  the  grounds  to  the  armor  at  the  end  of  the  two-conductor  cable 
the  continuation  of  the  armor  to  the  distant  end  of  the  cable  makes  one  of  the 
best  grounds. 

This  method  is  employed  by  the  Conunercial  Cable  Co.  at  New  York  City. 
The  two-conductor  cable  extends  10  miles  to  sea  from  the  beach  on  which  the 
commercial  cable  lands  near  New  York.  The  copper  core  to  the  ground  con- 
nection is  joined  to  six  different  iron  wires  to  insure  a  good  ground  connection, 
each  joint  and  all  copper  carefnlly  insulated,  and  each  of  the  six  iron  wires 
wrapped  around  the  armor  and  soldered. 


(466) 


I 


Long  Submarine  Cables,  Telegraphy,  and  Tests. — Chapter  11.  31 

CABLE  TESTING. 

The  remarks  appearing  in  this  manual  concerning  the  general  necessity  for 
testing  cable  regularly,  apply  with  added  force  in  the  case  of  long  submarine 
cables. 

By  applying  regular  tests  incipient  faults  will  frequently  disclose  themselves 
long  before  they  become  sufficiently  serious  to  interfere  with  the  working,  giv- 
ing ample  time  to  notify  the  repair  ship,  if  the  faults  are  out  at  sea.  Further- 
more, it  is  absolutely  necessary  in  case  of  cables  to  locate  them  accurately  by 
tests,  though  this  part  in  its  refinements  belongs  in  general  to  the  cable-ship 
experts.  The  subject  of  cable  testing  is  extensively  entered  into  by  Kempe  in 
his  Handbook  of  Electrical  Testing. 

The  works  already  cited  by  Wilkinson  and  Bright  also  describe  various 
methods.  Students'  Guide  to  Submarine  Cable  Testing  (Fisher  &  Darby), 
Electrical  Testing  for  Telegraph  Engineers  (J.  Elton  Young),  Beginners'  Manual 
of  Submarine  Cable  Testing  and  Working  (G.  M.  Baines),  and  Testing  of  In- 
sulated Wires  and  Cables  (Webb)  are  recommended  treatises  on  testing.  The 
Students'  Guide  and  the  three  latter  are  compact  treatises  which  are  quite 
elementary  and  easily  understood. 

It  is  proposed  to  describe  such  tests  as  are  usually  desirable  at  cable  stations. 

In  making  tests  using  delicate  testing  instruments  such  as  the  galvanometer, 
let  the  rule  be  to  begin  with  large  fraction  of  shunt  and  small  value  of  battery, 
gradually  decreasing  fraction  of  shunt  and  increasing  battery.  This  will  pre- 
vent damage  to  instruments  due  to  excessive  current  strength. 

In  making  the  approximate  measurements  at  stations  the  Weston  milllam- 
meter  and  voltmeter  set  may  be  used.  These,  of  course,  will  not'give  sufiiciently 
accurate  results  when  high-resistance  faults  exist.  The  Wheatstone  bridge  may 
be  used  whenever  measuring  the  ordinary  resistances,  and  the  ohmmeter  will 
answer  for  approximations.  The  Fisher  cable-testing  set,  described  later  in 
this  chapter,  combining,  as  it  does,  so  many  necessary  instruments  is  con- 
venient for  Morse  stations. 

The  reflecting  galvanometer  is  a  necessity  in  accurate  cable  measurements. 
Not  only  does  it  give  better  results  than  any  other  form  with  Wheatstone  bridge 
measurements,  but  it  is  a  necessity  in  insulation  resistance  and  capacity  meas- 
urements, both  of  which  are  very  important  in  cable  work.  Before  considering 
them  the  reflecting  or  mirror  galvanometer  will  be  described. 

BEFLECTING  GALVANOMETERS. 

Any  pointer  or  indicator  attached  to  the  movable  coil  or  needle  of  the  galva- 
nometer increases  the  mass  to  be  moved  and  decreases  the  sensitiveness.  A 
delicate  mirror  being  attached  to  the  coil  or  needle  may  be  used  to  reflect  a 
beam  of  light  onto  a  scale,  thus  giving  a  weightless  pointer  or  indicator  as 
long  as  may  be  desired  and  consequently  great  sensitiveness.  Another  way  of 
utilizing  the  reflecting  principle  is  to  view  the  reflected  image  of  the  scale  with 
a  small  telescope,  noting  the  number  on  the  scale  intersected  by  a  vertical 
thread  in  the  telescope.  Formerly  the  Thomson  reflecting  galvanometer  (fig. 
11-20)  was  exclusively  used  for  any  case  requiring  great  sensitiveness. 

The  beam  of  light  from  the  lamp  L  shining  through  the  slit  in  the  shield  Is 
reflected  from  the  mirror  attached  to  the  suspended  magnetic  needle  N  and 
projected  on  some  point  of  the  scale  S. 


(467) 


32 


Signal  Corps  Manual  No.  3. — Chapter  1  1 . 


The  needle  swings  in  a  small  space  in  the  middle  of  the  coils,  and  the  direc- 
tion and  stfenpth  of  the  controllinj;  force  is  given  by  the  bar  iiiauiH-t  .1/.  P>y 
(his  arrangement  it  is  seen  that  a  very  small  movciiicnt  of  the  nccdU'  ;iiid  ihe 
atiaclied  nnrror  will  ho  greatly  niagnilied  hi  the  niDNciiieiit  of  the  s|)ot  of  light 
on  the  scale. 


Fig.  11-20.— LONG     SUBMARINE    CABLES,    TESTING,     THOMPSON      REFLECTING     GAL- 
VANOMETER. 

The  Thomson  galvanometer  is  well  adapted  to  laboratory  work,  l)ut.  for 
testing  cables  after  they  are  laid,  where  there  are  always  some  disturbing 
(•urrents,  it  has  been  found  that  the  Sullivan  Universal  galvanometer  gives 
better  results;  it  is  not  so  sensitive  as  the  Thomson  but  is  more  "dead  beat" 
and  manageable.  The  coil  is  suspended  in  the  field  of  a  i)ermanent  magnet 
and  is  dampened  with  a  fine  brush. 


Fig.  11-21.— LONG    SUBMARINE    CABLES,    TESTING,     D'ARSONVAL    REFLECTING    GAL- 
VANOMETER. 


(KiS) 


Long  Submarine  Cables,  Telegraphy,  and  Tests. — Chapter   1  I . 


33 


Galvanometers  of  tlio  D'Arsouval  class,  witli  a  suspended  coil  turning  in  the 
field  of  Ji  p«'rmanciil  iiia.iiiict.  arc  in  ^'cncral  use  for  all  kinds  of  iiu'iisiirciiicnts. 
While  usually  iml  <>r  such  a  liiirh  dc;:i-cc  n\'  scnsitivoiU'ss  as  I  he  Thouisoii,  they 
are  much  more  "dead  heat"  and  niana.Lreahle.  These  are  (luite  pMierally  used 
as  mirror  galvanometers. 

An  excellent  form  for  cable-station  use  is  shown  in  figure  11-21.  As  will  be 
noted,  these  use  the  small  telescope  to  view  the  .scale  and  should  be  so  mounted 
tliat  the  liyht  from  the  window  or  lamp  will  fall  on  the  .scale. 

It  will  also  be  noted  that  this  instrument  is  practically  a  duplicate  of  the 
one  described  in  chapter  4  of  this  manual,  except  that  it  is  de.signed  for  mount- 
in??  permanently  or  semipermanently  on  a  wall  while  the  one  described  in 
chapter  4  is  equipped  with  a  tripod  in  order  that  the  instrument  can  be  con- 
veniently set  up  in  the  field. 


As  explained  in  chapter  4  of  this  manual,  any  delicate  galvanometers  like 
the  above  can  not  be  used  in  most  cases  with  the  whole  current  involved  in 
the  measurement,  as  even  through  a  very  great  resistance  a  single  cell  will 
cau.se  the  reflected  image  to  move  comiiletely  off  the  scale,  (consequently 
shunts  are  provided  which  allow  certain  definite  portions  of  the  current 
(usually  i'o.  -nnr-  "i"  r^^  t<»  P^i^^^  through  the  shunt,  and  tu,  tto.  »n<l  roW) 
respectively,  to  go  through  the  galvanometer. 


m 


999 


o  rMijlimrifTvis 


•  o 


Fig.  11-22.— LONG  SUBMARINE  CABLES,  TESTING,   SHUNT,   SIMPLIFIED   DIAGRAM. 

The  simplified  diagram  is  shown  in  figure  11-22. 

By  placing  the  plug  at  one  or  the  other  of  the  points  a  divided  circuit  is 
formed,  and  a  certain  part  of  the  current  will  flow  through  the  shunl  and  the 
other  through  the  galvanometer.  For  example,  ^  has  ^  as  much  resistance 
as  the  galvanometer.  So  -^  of  the  current  will  flow  through  this  and  yj^j 
through  the  galvanometer.  Hence,  the  deflection  with  this  shunt  will  be  only 
YSTS  as  much  as  it  woidd  be  if  no  plug  were  i)Ut  in  the  shunt  to  bring  the 
deflection   within   readable  limits. 


(4G0) 


34 


Signal  Corps  Manual  No.  3. — Chapter  11, 
Remarks  on  the  shunt. 


Resistance  of  shunt  compared  to 
resistance  of  galvanometer. 

Current  through— 

Whole 

current. 

Multi- 
plying 
power  of 
shunt. 

Shimt. 

Galva- 
nometer. 

1 

999 

1 
99 

1 

9 

No  shunt 

^       +       -^-      =          1 
1000                   KHM) 

^         +         i-        =            1 
100                     100 

1    +    1    =     1 

10            ^          HI 

0           +           1=1 

1,0(K) 
100 

10 

1 

^Multiply  the  deflection  of  the  galvanometer  hy  the  multiply in.a:  power  of  the 
shunt  to  obtain  what  the  true  deflection  woidd  he  with  lut  shunt,  wlien  all  cur- 
i-ent  passes  through  the  pilvanometer. 

Let  fi=Resistance  of  jj'ilvanonieter, 
K=Resistance  of  shunt, 
.l/=]\rultiplying  power  of  shunt, 


Then  .V=' 


-S 


S= 


SM=G+S 

G 

"J7-1 

Example:  Let  S=l  and  G=99 

Q9  +  1 
Then  J/=^^  =100 

^'  =  1X(10()— 1)=99 
99 


JS= 


100-1 


r=l 


Fig.  11-23.— LONG    SUBMARINE    CABLES,    TESTING,    AYRTON    UNIVERSAL    SHUNT. 

(-47(1) 


Long  Submarine  Cables,  Telegraphy,  and  Tests. — Chapter  11.  35 


I 


Goiv  920co 


Fig.  11-24.— LONG    SUBMARINE    CABLES,    TESTING,    AYRTON    SHUNT,    CONNECTIONS 

Tlio  Ayrton  universal  shunt  (figs.  11-23  and  11-24)  is  now  frequently 
u.-ied  witli  galvanometers  of  moderate  resistances.  One  of  these  can  be  used 
with  any  galvanometer  regardless  of  their  relative  resistances,  and  it  has  the 
advantage  of  being  accurate  for  condenser  and  capacity  measurements  as  well. 
In  this  the  shunts  are  more  conveniently  marked  rwisui  tsttj  Ti>  t- 

The  principle  of  the  Ayrton  universal  shunt  is  that  where  the  resistance  of 
the  galvanometer  is  small  in  comparison  with  the  total  resistance  of  the  shunt 
the  resistance  of  the  galvanometer  is  ignored. 

J/=Multiplying  power  of  shunt. 
G=Resistance  of  the  galvanometer. 
/S=Resistance  of  the  shunt. 


M= 


G+S 


Consider  that  resistance  of  the  galvanometer  itself  is  zero  and  that  the  pluj 
is  in  the  xTjVff  *^'i^i"t,  where  the  nudtiplying  power  is  1,000,  then: 


1000= 


G+S 
S 


Call  that  part  of  the  shunt  in  series  with  the  galvanometer,  the  resistance 
of  the  galvanometer,  or  3.600+360+36=3,996  ohms,  and  the  resistance  of 
the  actual  shunt  A'. 

Then  ]00n=^^A+ ^  or  1000  A'=3996+A'  or  999  A'=3996,  where  A'  or  the  shunt 

equals  4  ohmi5. 

Substituting  4  ohms  for  S  and  3996  for  (i: 

T.I       •        ,       .1         ^r    3996+4  4000        ,,     ,  „„„ 

Plug  in  rrhn^  tlien  J/= .-^-      or  — —  or  J/=1,000 

T>i        •        1       +t  ^f    3960+40         4000        ,,     i,,„ 

Plug  in  -i^js,  then  M= — ^~-    or  ~—  or  J/=100 

T>i        •        1       *i,         ^r    3600+400       4000        ,,     ,(, 
Plug  in   A,    then  .1/=       ^^^       or-^-  or  .V=10 


111        •        1      *v,        1^    0+4000 
Plug  in     1,     then  -V=-^^^^ 


4000        „    , 
"'•4000«'^-^^=^ 


(471) 


36  Signal  Corps  Manual  No.  3. — Chapter  11. 

The  miiltiplyinj;  power  is  proved  in  eacli  case,  and  it  can  also  be  seen  that 
the  following  rule  in  the  Sullivan  marine  galvanometer  shunt  is  proved,  i.  e. — 

To  obtain  the  multiplying  power  of  the  shunt,  divide  the  total  resistance 
in  the  shunt  by  the  amount  of  the  shunt  cut  in. 

As  an  actual  fact,  though,  the  galvanometer  in  the  Fisher's  set  at  Seattle 
has  920  ohms  resistance,  adding  that  also  to  the  G  resistance  used  in  the 
examples  above,  the  following  results  are  obtained,  showing  that  even  920 
ohms  in  the  galvanometer  itself  can  be  ignored,  and  the  Sullivan  rule  is 
again  proved : 

■D,       •        1       .1         If    3996+920+4  4920        ,,    ,.,.,^ 

Plug  in  xTnnr.  "len  J/= -i- '—       or  -— -  or  J/=1230 

T>i-  •   •       ,41         ^f    3960+920+40  4920    „  ,,    ,.,., 

Plug  m  -j^,  then  M= '—- — ■ —     or  —  —  or  J/=123 

1,1        ■        1     ,1  If    3600+920+400    „  4920        ,,    ,.,  ^ 

1  lug  in    ■^,  then    M— -r?.-^ or  -^-^  or  M=12.  3 

^'  400  400 

-Di        •       1      ♦!,  If    0+920+4000  4920        ,,     ,  .,^ 

Plug  in    1,    then    M= — ■ — -— !- or  — --  or  Ji=1.23 

4000  4000 

From  the  last  set  of  examples,  where  the  galvanometer  has  an  actual  re- 
sistance, nearly  one-fourth  that  of  the  shunt,  it  is  found  that  though  M  is  1, 
it  should  really  be  1.23 ;  yet  the  multiplying  power  of  10,  100,  and  1000  is 
exact,  considering  the  M  for  1  as  the  unit  whatever  it  may  be.  Therefore, 
the  relation  is  the  same  as  in  the  first  set  of  values,  where  the  galvanometer 
itself  had  no  resistance. 
For—  1  times  1.23=1.23 

10  times  1.23=12.3 
100  times  1.23=123 
1000  times  1.23=1230 

and  the  multiplying  power  is  unchanged  by  counting  or  not  counting  the 
resistance   of   the   galvanometer. 

Another  form  of  Ayrton  shunt  is  shown  in  chapter  4  and  is  siiecially  adapted 
for  portable  testing  sets.  With  the  latter  type  the  circuit  key  is  made  a  part 
of  the  apparatus.  It  will  be  noted  that  with  these  shunts  the  fractional  di- 
visions are  1,  0.1,  0.01,  0.001,  0.0001.  The  latter  fractional  division  is  a  con- 
venient addition  when  observing  galvanometer  constant,  using  one-tenth  megohm 
as  known  resistance,  as  by  its  use  the  full  voltage  of  testing  battery  can  be 
used  with  De  Arsonval  galvanometers  having  a  sensibility  approximate  to 
those  usually  furnished. 

The  method  of  making  lueasurements  of  insulation,  capacity,  and  oliiuic  re- 
sistance, using  instruments  furnished  with  the  Signal  Corps  electrical-instru- 
ment case,  are  fully  described  in  chapter  4  of  this  manual.  Inasmuch  as  tests 
on  lonjj  submarine  cables  using  the  same  type  instruments  would  be  similarly 
made,  a  repetition  of  the  description  would  bo  superfluous.  However,  with  long 
subinarin(>  calilcs  great  care  must  be  exercised  to  avoid  doing  anything  that 
will  impair  the  insulation.  The  voltage  used  in  making  tests  nnist  be  kept  as 
low  as  is  j)osslble  to  attain  desired  results.  Readings  should  be  taken  with 
positive  pole  of  battery  to  ground  and  IIkmi  with  negative  pole  to  ground. 
Should  there  be  a  variation  in  these  readings,  Ihe  mean  of  the  two  should  be 
nccei)(e(l  as  true  reading. 

When  tlie  cable  exceeds  100  miles  in  length,  caparity  measurements  should  be 
made  by  Thomson's  or  Gott's  methods.  Descriptions  of  these  are  found  in  the 
books  of  references. 

(472) 


Long  Submarine  Cables,  Telegraphy,  and  Tests. — Chapter  1  I , 


37 


I'M.mirc  11-25  sliows  soiiio  of  llio  specnal  instrunn'nts  used  in  .sul»iii;iriiie-cal)lu 
testing  at  (•al)lo  oflicos  of  the  NN'asliington-AUiska  Military,  Cable  and  Tele^'rapli 
System. 


Discharge  Key  for  measuring  capacity 


High-insulation  Binding  Posts  Double  Plug  Switch 

Fig.  11-25.— LONG  SUBMARINE  CABLES,  TESTING,  SPECIAL   INSTRUMENTS  USED. 

If  the  piece  of  cable  to  be  measured  i.s  short,  its  insulation  resistance  will 
probably  be  very  hij,'h,  and  a  battery  of  from  50  to  100  cells  in  series  will 
be  required.  These  may  be  the  smallest-size  dry  cells,  or  one  of  the  resrular 
boxes  of  testing  batteries.  The  regular  testing  battery  is  composed  of  chloride 
of  silver  cells.  On  account  of  their  first  cost  and  liability  to  be  ruined  by  even  a 
brief  short  circuiting,  it  is  advisable  1o  reserve  this  type  of  liattery  for  insula- 
tion measurements  onlv. 


(473) 


38 


Signal  Corps  Manual  No.  3. — Chapter  11. 


CONDUCTOB  KESISTANCE. 

This  is  usually  called  "copper  resistance"  (C.  R.)  in  books  on  cable  testing. 

To  measure  the  resistance  of  sound  cable  when  it  is  coiled  in  the  tanks,  when 
both  ends  are  available  the  methods  before  given  and  cited  in  reference  books 
may  be  followed.  Of  course,  the  most  satisfactor-y  and  accurate  method  is  with 
some  form  of  Wheatstone  bridge  and  mirror  galvanometer  when  these  instru- 
ments may  be  had.  Good  approximations  may  be  made  with  the  ohmmeter,  or 
the  combination  of  voltmeter  and  milliammeter,  as  stated  in  land-line  testing. 
It  is  evident  that  if  we  know  the  resistance  of  the  cable  per  mile,  and  find  the 
total  resistance  of  the  cable,  the  length  of  it  is  equal  to  the  total  resistance 
divided  by  the  resistance  per  mile.  This  method  is  called  to  attention  because 
of  its  constant  use  in  determining  the  lengths  of  pieces  of  single  conductor 
cable.  Of  course,  the  temperature  must  be  taken  into  account,  and  the  resist- 
ance measured  must  be  reduced  to  that  at  the  temperature  at  which  the  resist- 
ance per  mile  is  stated.     A  table  of  temperature  coefficients  is  given  below. 


Temperature  coefficients  for  copper  resistance. 


Difference  in 

Difference  in 

degrees— 

Coeffi- 
cient. 

degrees— 

Coeffi- 
cient. 

Faliren- 

Centi- 

Faliren- 

Centi- 

heit. 

grade. 

lieit. 

grade. 

1 

0.5 

1.002 

16 

8.9 

1.034 

2 

1.1 

1.004 

17 

9.4 

1.036 

3 

1.7 

1.006 

18 

10 

1.0385 

4 

2.2 

1.008 

19 

10.5 

1.041 

5 

2.8 

1.010 

20 

11.1 

1.043 

6 

3.3 

1.013 

21 

11.6 

1.045 

7 

3.9 

1.015 

22 

12.2 

1.047 

8 

4.4 

1.017 

23 

12.7 

1.049 

0 

5 

1.019 

24 

13.3 

1.051 

10 

5.5 

1.021 

25 

13.8 

1.054 

11 

6.1 

1.023 

26 

14.4 

1.056 

12 

6.6 

1.025 

27 

15 

1.058 

13 

7.2 

1.0275 

28 

15. 5 

1.060 

14 

7.7 

1.030 

2!) 

16 

1.062 

15 

8.3 

1.032 

30 

16.6 

1.065 

In  using  this  table  note  that  in  passing  from  a  higher  to  a  lower  tempera tur(> 
divide  the  observed  resistance  by  the  number  opposite  the  degrees  of  difference 
of  temperature,  and  in  passing  from  lower  to  higher  multiply  the  same. 

Example:  A  piece  of  cable  is  measured  at  8")°  F.  and  has  a  resistance  of  1(K» 
ohms.  Tilt!  resistance  per  mile  (9.5  ohms)  is  giv(>ii  at  7.5°  F.  The  difference  is 
10°  F.  higher  than  the  standard. 

100-^1.021^97.94  ohms  a  1  7.5°  F. 

and  the  length  of  the  piece  is  97.94-^-9.5 —  10.31  miles. 

While  tlie  length  of  single-conductor  cable  can  be  ascertain(\l  accurately  by 
this  iiicIIkmI,  it  has  been  the  author's  experience  that  with  nuiltiple-conductor 
twiste(l-j)air  cable  only  an  approximation  of  the  length  can  be  obtained,  because 
on  account  of  the  twists  and  lay  the  conductors  are  actually  longer  than  cable. 
Not  only  are  pairs  twisted  together,  bill  llie  i»airs  are  wound  spirally  around 
-the  longitudinal  center. 

After  laying  the  cable,  in  attempting  to  measure  its  resistance*  through  (he 
ground  cotmections  at  each  end  the  simplicity  vani.shes  of  measuring  with  the 
Wheatslf>ne  bridge  and  balancing  until  the  galvanometer  is  at  zero.  It  will  be 
found  that  after  making  connections  and  before  depressing  the  battery  key 


(•174) 


Long  Submarine  Cables,  Telegraphy,  and  Tests. — Chapter  1  I 


39 


tlinf  if  we  depress  the  short-eircuit  key  a  tleflectioii  will  generally  be  noted. 
This  is  largely  due  to  earth  current  (called  K.  C.  in  reference  books).  If  it 
were  steady  it  could  easily  be  dealt  with.  Unfortunately,  it  is  not,  and  it  is 
constantly  varying  in  direction  as  well. 

Two  ways  of  measuring  to  eliminate  earth-current  effects  are  de.scribed  in 
works  on  cable  testing  called,  respectively,  "Quick  reversals "  and  "False 
zero."  (See  pp.  59-62,  3d  ed..  Students'  Guide  to  Submarine  Cable  Testing, 
Fisher  &  Darby.)     A  brief  additional  description  of  these  may  be  useful. 


r 

Fig.  11-26.— LONG    SUBMARINE    CABLES,    TESTING,    COPPER     RESISTANCE,    CONNEC- 
TIONS. 

Tonnections  for  measuring  coiijier  resistance  are  shown  in  tigure  11-116. 
A  Ji  is  the  reversing  key,  C  is  the  Wheatstone  bridge,  G  is  the  galvanometer,  S 
the  universal  shunt,  A'  the  short-circuit  key,  F  the  testing  battery.  The  bridge 
is  connected  with  the  cable  conductor  E,  prepared  as  shown,  and  A  and  the 
bridge  are  connected  to  a  brightened  place  on  the  cable  armor  wires  for 
ground  connections,  as  explained  under  "  Capacity  measurements."  Of  course 
in  this  case  the  distant  end  of  conductor  is  connected  with  the  armor  wires 
or  ground.  As  will  be  seen,  by  depressing  B  the  copper  (or  carbon)  end  of 
the  battery  will  remain  connected  with  the  ground,  while  the  zinc  goes  to 
cable  conductor  through  the  bridge.  Due  to  tlie  fact  that  the  "  zinc  current," 
as  it  is  called,  tends  to  clear  away  corrosion 'when  measuring  to  locate  a  fault, 
measurements  made  with  it  usmUly  show  lower  resistances  than  when  carbon 
or  copper  is  put  to  line  by  depressing  ^1.  However,  as  little  effect  of  this 
kind  will  be  noted  in  sound  cable  with  distant  end  well  connected  with  ground 
as  stated,  we  shall  assume  disturbances  due  only  to  earth  currents  in 
measuring. 

The  method  by  quick  reversals  will  lirst  be  described.  Depress  Ji,  wait  a 
second  or  two,  and  depress  K.  Balance  as  rapidly  as  possible,  noting  re- 
sistance. Release  7?,  then  depress  .1  and  A',  and  again  balance  quickly.  The 
mean  of  these  resistances  will  give  the  one  approximately  correct,  unless  there 
is  too  great  a  difference  between  them,  in  which  case  the  correction  on  page 
56,  3d  ed.,  Fisher  &  Darby,  should  be  applied. 

Balancing  to  false  zero  (F.  Z.)  is  the  usual  method  of  providing  for  earth 
currents  in  measurements  of  conductor  (copper)  resistances  of  cable. 


46581^—17- 


-31 


(475) 


40 


Signal  Corps  Manual  No.  3. — Chapter  1  I. 


Before  depressing  A  or  B,  if  we  depress  tlie  sliort-circuit  key  we  shall  gener- 
ally note  a  deflection.  This  is  due  to  the  earth  current.  Suppose  it  to  be  fairly 
steady,  its  direction  and  amount  should  be  noted.  If  variable,  its  mean  in  the 
time  usually  occupied  by  balancing  should  be  noted.  This  is  the  false-zero  posi- 
tion to  which  we  balance,  instead  of  the  true  or  instrumental  zero  we  have 
heretofore  considered.  If  the  earth  current  or  false  zero  is  constantly  varying, 
it  should  be  noted  just  before  and  just  after  taking  a  measurement,  and  the 
false-zero  position  taken  as  the  mean.  Several  measurements  should  be  made 
until  several  successive  results  are  obtained  which  accord  fairly  well.  A  good 
measurement  of  the  copper  resistance  of  the  sound  cable  is  an  absolutely  nei'es- 
sary  preliminary  lo  the  location  of  faults  when  they  occur. 

The  usual  form  t)f  Wheatstone  bridge  used  at  Alaskan  cable  stations  is  shown 
in  figure  11-27. 

The  form  of  report  below  illustrates  the  manner  of  tabulating  tlata  pertain- 
ing to  long  submarine  cables. 

The  data  which  follows  illustrates  the  character  of  report  turned  in  on  com- 
pletion of  cable. 

BECOKD    OF    CABLK    TESTS. 


U.    S.    SIGNAL    CORPS. 


Date 

Tests  made  by 

Submarine  calile  num.ber- 


Place. 


-between and. 


Gfilvanonieter  constant. 
(Through  100,000  ohms.) 


Kind  of  galvanometer Voltage  of  battery. 

fRight- 

Shunt Deflection  i  Left__. 

[Mean-. 
Constant  per  volt. 


INSULATION. 

Cable  current:  Deflection (right  or  left),  with  shunt. 

Voltage  of  battery Shunt 


Deflections. 


1st  min. 
2d  min.. 
3d  min.. 
•1th  min. 
otb  min . 


Zinc. 


Carbon. 


Mean. 


-Vb.soluto  insulaliun  cud  of  throe  minutes. 


COPPKR  RESISTANCE. 

Deneclion 

Earth  current with  .shimt 

VoltaRo  of  battery JJridge  ratios 

Kcsistanoo,  zinc  to  line 

K<isi.st;uice,  carbon  to  line 

Meiin 

The  records  show  that  the  resistance  should  lie  -  -  ohms. 
Capacity  measurements  mu<ie  when  directeii. 

\OTE.— Connect  Ralvanometer  .so  that  with  zinc  to  line  in  insulation  test  the  deflection  will  be  to  left. 
One  copy  of  this  record  will  be  retained  and  three  mailed  to  the  oflicer  in  charge. 


(47t;> 


Long  Submarine  Cables,  Telegraphy,  and  Tests. — ^Chapter 


41 


DATA    PERTAIXING    TO    THE    SITKA-SEATTLE    CABLE    WHEX    IT    WAS    LAID. 

(This  data  is  sho^vn  as  an  e.xample  to  be  followed.) 


i 


Type. 

Nautical 
miles. 

C.  K.  60°. 

C.  R.  tem- 
perature 
at  bottom. 

Sitka- 
Seattle. 

Seattle- 
Sitka. 

Temper- 
ature at 
bottom. 

S.  E.  Sitka,  1903 

1.987 

6.533 

9.040 

11.672 

6.768 

7.800 

4.914 

43.365 

61.264 

40. 179 

19.378 

59.298 

50. 172 

5.050 

21.780 

63.370 

14.860 

6.770 

2.470 

54.470 

17.000 

91.170 

12.900 

13.060 

2.800 

17.440 

.968 

1.832 

20.650 

20.310 

22.200 

21.540 

8.910 

3.718 

32.230 

14.  702 

24.386 

9.800 

11.020 

10. 970 

10.950 

11.370 

4.660 

1.110 

16. 420 

5.760 

14.020 

8.000 

7.700 

2.600 

Ohms. 

16.92 

55.66 

77.02 

99.44 

57.66 

66.45 

41.86 

369. 46 

521.97 

342. 33 

165.10 

505.22 

427. 46 

43.03 

185.56 

539.91 

126.60 

57.68 

21.04 

464.08 

144.84 

776.  77 

109.90 

111.27 

23.85 

148.59 

8.25 

15.60 

175.94 

173.04 

189. 14 

183.52 

75.91 

31.67 

274. 60 

125.26 

207.77 

83.50 

93.89 

93.46 

93.29 

96.87 

39.-70 

9.45 

139.90 

49.07 

119.45 

68.16 

65.60 

22.15 

Ohms. 

16.38 

53.89 

74.57 

96.28 

55.82 

64.33 

40.17 

354.60 

496.59 

325.68 

157.07 

480.65 

406.67 

40.93 

176.53 

513.66 

120.44 

54.87 

20.01 

441.51 

137.  79 

739.00 

104.55 

105.86 

22.69 

141.36 

7.85 

14.83 

167.38 

164.62 

181.53 

176. 14 

73.50 

30.66 

265.87 

121.28 

201.17 

80.84 

90.91 

90.49 

90.32 

93.79 

38.44 

9.15 

135.45 

47.51 

115.66 

66.00 

63.52 

21.45 

Ohms. 
16.38 

70.27 
144.84 
241.12 
296.94 
361. 27 
401.44 
756.04 
1,252. 63" 
1,578.31 
1,735.38 
2, 216. 03 
2,622.70 
2,663.63 
2,840.16 
3,353.82 
3,474.26 
3,529.13 
3,549.14 
3,990.65 
4,128.44 
4,867.44 
4,971.99 
5,077.85 
5,100.54 
5,241.90 
5, 249. 75 
5,264.58 
5,431.96 
5,596.58 
5, 778. 11 
5,954.25 
6,027.75 
6, 058. 41 
6,324.28 
6,445.56 
6, 646. 73 
6, 727. 57 
6,818.48 
6,908.97 
6,999.29 
7,093.08 
7,131.52 
7,140.67 
7,276.12 
7,323.63 
7,439.29 
7, 505. 29 
7,568.81 
7,590.26 

Ohms. 

7,590.26 

7,573.88 

7,520.49 

7, 445. 42 

7,349.14 

7,293.32 

7,228.90 

7,188.80 

6,834.22 

6,337.60 

6,011.90 

5,854.88 

5,374.23 

4,967.56 

4,926.63 

4, 750. 10 

4,236.44 

4,116.00 

4,061.13 

4,041.12 

3,599.61 

3,461.82 

2,722.82 

2,618.27 

2,513.41 

2,489.72 

2,348.36 

2,340.51 

2,325.68 

2,158.30 

1, 993. 68 

1,812.15 

1,636.01 

1,562.51 

1,531.85 

1,26.1.98 

1,144.70 

943.53 

862. 69 

771.  7S 

681.29 

590.97 

497. 18 

458.74 

449.59 

314.14 

266.63 

150.97 

84.97 

21.45 

'F. 
45 

Inter.,  1903 

45 

Do 

45 

Do 

45 

Deep-sea,  1903 

45 

Do 

45 

Do 

41 

Do 

41 

Do 

37 

Do 

37 

Do 

37 

Do 

Do 

Do 

Deep-sea,  1904 

Deep-sea,  1903 

Do!;;;!!;!!;;;:;!;;;;;;;;;;!;; 

Deep-sea,  1904 

Deep-sea,  1903 

Do 

Do 

Do 

37 
37 
37 
37 
37 
37 
37 
37 
37 
37 
37 
37 

Do 

Do 

37 
37 

37 

Deep-sea,  1904      

37 

Do 

37 

Do 

Do 

37 
37 

Do 

41 

41 

Do 

45 

Inter.,  1903 

45 

Do 

Do 

Do 

45 
45 
45 

45 

Do  

45 

Do 

45 

Do                    

45 

Do 

45 

Inter.,  1903                         

45 

Inter.,  1901 

45 

Inter.,  1903 

45 

Do                    

45 

Do 

45 

Deep-sea,  1904 

45 

Inter.,  1903 

45 

S.  E.  Seattle,  1903         .        .     . 

45 

Total 

931.336 
4.477 

7,934.96 
40.43 

7,590.26 
39.26 

Earth  Seattle 

Total 

935. 813 

7,975.39 

7,629.52 

Ohms. 
K .  from  buov  to  Sitka 7,496. 000 


C.  K .  from  buoy  to  Seattle  through  office  to  dock. 

Total 7, 590. 617 

C".  K .  of  Seattle  ground  end 39. 265 

Total 7,629.882 

Average  D.  R.,  absolute  2.25 megohms;  2,104  megohms  pernautical  mile. 

rapacity  "1903 type" 737.ir.fi  nautical  miles,  at  0.593=437  microfarads. 

Capacity  "  1904 1  vpe" , .  lS:3.s^>0  nautical  miles,  at  0.472=  87  microfarads. 

Seattle  shore  end  to  dock 6  microfarads. 

Total  capacity  by  r.ott's  method  from  Arlington  Dock  to  Sitka,  Alaska 530  microfarads. 

Average  temperature,  Seattle  to  Sitka,  39.1°  F. 
Distance  on  charts,  Seattle  to  Sitka,  856  nautical  miles. 


(477) 


42 


Signal  Corps  Meinual  No.  3. — Chapter  11. 


Fig.  11-27.— LONG    SUBMARINE    CABLES,   TESTING,  WHEATSTONE    BRIDGE. 

DESCRIPTIOX   OF   FISHER  CABLE-TESTING   SET   NO.    2. 

Note. — In  all  measurements,  with  this  set,  let  the  rule  be  to  begin  with  large  fractional  value  of  shunt 
and  small  battery,  gradually  decreasing  the  shunt  and  increasing  the  battery. 

This  set  .shown  in  figure  11-28  was  originally  designed  by  Mr.  H.  W.  Fisher. 
It  is  intended  for  work  where  a  strictly  portable  set  is  required. 

As  it  will  frequentl}'  be  used  for  locating  trouble,  a  special  arrangement  of  the 
bridge  has  been  adopted  so  as  to  greatly  facilitate  Murray  &  Varley  loop  tests 


Fig.  11-28.— LONG  SUBMARINE  CABLES,  TESTING.  FISHER  CABLE  TESTING  SET  NO    2. 

(47S) 


Long  Submarine  Cables,  Telegraphy,  and  Tests. — Chapter   1  1 .  43 

for  faults.  Mr.  Fisher  lias  also  inlroduccd  a  method  new  to  portahle  eable 
icstiiif;  sets  for  locating;  hi'caks  in  cables  wiiere  tlie  conductor  has  parted;  and, 
ill  addition  to  the  usual  one,  a  new  method  for  measuring;  capacity  in  which 
no  j,'alvanometer  is  i-(H|uired,  a  teh'plione  Itein^  \isfd  in  phice  of  it. 

Tlie  i)arts  are  moimted  on  corrugated  liard-rul»l)er  pillars,  which  extend  above 
and  below  the  base. 

This  tirrangement  gives  ii  very  good  insulation,  and  one  that  will  be  found 
entirely  satisfactory,  except  under  the  most  trying  condition  of  moisture.  The 
changes  from  one  test  to  another  are  acconiplished  very  easily  and  without  the 
use  of  inconvenient  flexible  cords.  They  are  effected  by  double-throw  switches 
whicii  are  plainly  marked  so  that  it  is  not  necessary  to  memorize  a  complicated 
sclieme  of  connections. 

Tlic  standard  of  capacity  has  a  single  value  of  ttj  microfanid. 

The  standard  high  resistance  is  1( ){),(»( K)  ohms,  and  is  also  a  single  value,  not 
subdivided. 

In  the  Wheatstone  bridge  u  marked  variation  from  the  usual  commercial 
type  has  been  made.  The  change  is  introduced  to  facilitate  measurements  for 
the  location  of  faults.    It  is  an  extension  of  the  Kelvin-Varley  slides,  and,  since 


lo  ,  S>  3  *  S  6  7  a  *  I 

OvvwvQvvvvvOwv^OvvvvviOwvvvvQ^^^^ 

\       O  /  »  3  ^  £  6  7  e 

iQwvmO^wvvOvvmvO^v 


T£-/VS 


Fig.  11-29.— LONG  SUBMARINE  CABLES,  TESTING,   FISHER  CABLE  TESTING  SET  NO.  2. 
WHEATSTONE    BRIDGE    ARRANGEMENT. 

it  may  not  be  generally  known,  the  following  description  is  given.  It  is  a  form  of 
Wheatstone's  bridge  resembling  those  having  a  slide  wii'e  in  which  the  values 
of  the  rheostat  are  fixed  and  the  two  arms  of  the  bridge  are  varied  until  a 
lialance  is  effected.  The  arrangement  is  represented  in  diagram  in  figure  11-29. 
The  points  marked  G  and  B  are  the  points  of  attachment  for  the  galvano- 
meter and  battery,  i*espectively.  At  R  are  represented  the  four  coils  of  the 
rheostat,  any  one  of  which  may  be  used,  and  at  .Y  the  unknown  resistance. 
Between  M  and  2V  are  eleven  coils  of  equal  value,  which  form  the  bridge  wire. 
There  is  a  contact  point  between  each  coil  and  the  one  next  to  it.  The  other 
coils  shown  in  the  series  marked  "  Tens  "  and  "  Units  "  are  used  to  subdivide 
the  coils  of  the  bridge.  They  constitute  what  may  be  called  an  electrical  vernier, 
by  means  of  which  the  bridge  wirie  is  subdivided  to  thousandths  of  its  total 
value.  The  two  arrows  in  contact  with  the  points  marked  1  and  3  in  the  "  Hun- 
dreds "  row  and  with  the  2  and  4  in  the  "  Tens  "  row  represent  contact  arms 
which  can  be  moved  along  to  make  contact  at  any  of  the  contact  points,  but  are 
always  at  the  same  distance  apart,  so  that  they  have  two  coils  between  them, 

(479) 


44 


Signal  Corps  Manual  No.  3.— Chapter  11. 


IhCn 


•;'7fftc 


felD^c^^^^g© 


J  78^0 


^ 


^    ^    ^  o 


=c3 


050 


G-(D 


iPq! 


o  .^^^o 

050 


o 


Q 


0.0  ©,® 


@)^(§)<vi@>(g)«o(6) 


(480) 


Long  Submarine  Cables,  Telegraphy,  and  Tests. — Chapter  II.  45 

Tlioy  are  cnnnefted  t<»  tlio  ends  of  the  row  of  coils  below  them,  so  that  these 
Iwfi  coils  arc  slniiited  with  the  entire  row  of  coils  below.  Consider  now  the 
i-esull  of  lliis  sliuntinn  in  the  case  of  the  "Tens"  and  "Units"  colls.  The 
ti'ns  are,  for  example,  11  coils  of  80  ohms  each.  The  units  are  10  coils 
of  16  ohms  each.  The  two  8()-ohm  coils  l)etween  the  points  2  and  4  ar«' 
shunted  with  the  10  IG-ohm  coils;  160  ohms  is  shunted  with  160  ohms,  and 
the  resistance  lietween  the  points'  2  and  4  becomes  80  instead  of  100  ohms. 
There  are  in  the  "Tens"  series,  for  any  posiiion  of  tlie  double  arms,  actually 
10  resistances  of  80  ohms  each.  The  point  of  galvanometer  contact  may  be 
placed  at  any  position  in  the  "Units"  series,  thus  subdividing  the  shunted 
coils  in  the  "  Tens "  series  to  tentlis.  The  coils  in  the  "  Hundreds "  series 
are  400  oluns  each,  and  are  subdivided  in  tlie  same  way  by  tliose  in  the  "  Tens  " 


Q   a33G^ 


MUNOfieOS. 


BA  ¥\     6 A "  '"  '"'I 


Fig.  11-31.— LONG  SUBMARINE  CABLES,  TESTING,   FISHER  CABLE  TESTING  SET  NO.  2 

CONNECTIONS. 

series.  An  example  will  make  tlu^  use  of  the  bridge  clear.  Assume  that  a 
balance  is  obtained  with  100  unplugged  in  the  rheostat  and  the  contacts  in 
the  position  shown.     The  bridge  reading  is  then  287.     Call  this  value  .4.     Then 

X:R::A:\,m)-A,  and  X=i?-— ^ j=100|H=31.06. 

l,UtX)  —  A. 

The  calculation  of  the  fraction  ff^  would  take  considerable  time  and  might  lead 
to  errors.     To  overqome  the  necessity  for  this  we  furnish,  conveniently  fastened  into 

for  all  values  of  A  between 


the  lid  of  each  set,  a  table  giving  the  values  of 


1,000-^ 


0  and  1,000.     Reference  to  the  table  shows  -~^ — -=0.3106  for  ^=237.    We  have, 

1,000  — .4 

(481) 


46 


Signal  Corps  Manual  No.  3. — Chapter  11. 


consequently,  simply  to  multiply  the  value  taken  from  the  table  by  the  re- 
tsistante  luiplugged  in  the  rheostat  to  determine  the  value  of  X.  From  this 
it  will  be  seen  the  Wheatstone  bridge  measurements  may  be  made  and  cal- 
culated very  rapidly. 

In  the  actual  construction  the  coils  are  arranged  in  three  dials.  The  contact 
arms  and  points  are  constructed  so  as  to  insure  good  contacts. 

From  the  plan  (fig.  11-30)  and  the  diagram  (fig.  11-31)  the  arrangement 
and  connection  of  the  different  instruments  making  up  the  set  will  be  evident. 
Complete  information  in  regard  to  the  measurements  for  whicli  the  set  may  l)e 
used  can  be  ol)tained  from  the  following  directions: 

MEASIREMENTS     OF    ELECTROSTATIC     CAPACITY. 

In  making  tests  of  this  nature  a  reflecting  galvanometer  should  be  em- 
ployed, because  the  galvanometer  of  the  testing  set  is  not  suthciently  accurate, 
nor  has  it  a  long  enough  scale  to  give  good  results.  A  reflecting  galvanometer 
should  therefore  be  connected  to  the  posts  marked  Ga.     (Figs.  11-30  and  11-31.) 

A  few  cells  of  battery  can  be  connected  to  the  posts  Ba  by  means  of  the 
flexible  cords  which  come  out  through  the  hard  rubber  opposite  said  posts. 
If  a  larger  battery  is  required  the  flexible  cords  should  be  disconnected  from 
the  battery  of  the  set   and  connection   from   any  other  battery   made  to   the 


<x   o-<=oi^^SH7: 


Standard  Conden 


I 


Fig.  11-32.— LONG    SUBMARINE    CABLES,    TESTING,    MEASURING    ELECTROSTATIC 
CAPACITY,    SIMPLIFIED     DIAGRAM. 

posts  marked  Ba.  ('onnect  the  two  leading  wires  running  from  the  conductor 
of  the  cable  and  from  the  ground  to  "  cable  posts  "  and  insert  a  plug  in  the 
hole  marked  1  of  the  shunt.  Place  the  handles  of  the  two  double-throw 
swilclies  in  the  direction  of  the  letters  marked  "  C  or  /  ",  In  this  test  the  key 
marked  Ba  serves  to  close  the  battery  circuit,  the  contact  point  being  held 
in  ithice  by  the  linger  or  by  i)ressing  down  the  cam  lever  at  the  side  of  the 
key.  The  key  marked  Ga  serves  as  a  short-circuit  key  in  this  test,  and  the 
short  circuit  is  reuK^ved  from  the  galvanometer  by  pressing  the  key  down  or 
by  the  u.se  of  the  cam  lever.  Insert  two  plugs  in  the  holes  marked  C,  and  be 
sure  that  no  plugs  are  inserted  in  the  holes  marked  /  nor  in  the  hole  marked  G. 
The  test  can  now  be  made  in  the  ordinary  mniiner,  as  follows: 
I'ress  down  the  key  marked  Ba  for  about  10  seconds,  or  whatever  the 
required  time  of  charging  may  be,  and  tiie  instant  before  releasing  it  press 
down  tiie  key  marked  da  to  remove  the  short  circuit  from  the  galvanometer. 
Then  tiie  Ba  key  <'an  bo  released  and  the  discharge  deflection  of  the  gal- 
vanometer read.  If  it  is  too  small,  api)ly  more  battery  until  a  sufficiently 
large  detlecticHi  is  oIjImIiumI,  wliicii  record.  Next  disconnect  the  cable  lead 
wire.s  from  the  conductor  and  in  like  manner  measure  the.  discharge  deflec- 
tion due  to  the  leading  wires.  Then,  -without  in  any  way  changing  or  dis- 
<-onne<'liiig  the  leading  wires,  insert  a  |ilug  at  //  to  coniUM-t  the  0..'{  microfarad 
rondciiscr  across  tlH-  cable  jxists,  and   in   like   manner   read   the  (liscliarge  de- 

(482) 


f 


Long  Submarine  Cables,  Telegraphy,  and  Tests. — Chapter   11.  47 

flection  of  the  condenser.     It  is  not  necessary  to  jam  the  plug  too  tightly  in 
place,  because  in  doing  so  the  hard-rubber  posts  may  be  strained. 

To  obtain  the  true  discharge  deflection  of  cable  and  condenser,  siiiitnict 
the  dischargi!  (h-fiection  due  t<>  the  leading  wires  from  the  oi)served  discharge 
deflection  of  cal)le  and  condenser. 

Deflections  are  proportional  to  the  capacities ;  the  proportion  is  direct.  Then 
letting 

l//*'=Microfards. 
A'^= Number  of  cells. 
i1/=Multlplying  power  of  shunt. 

X=Cnpacity  and  D=Deflection  of  Icnown  capacity  discharge. 
Z=Capacity  and  /)'— Deflection  of  uniinown  capacity  discharge. 
7j=Length  of  cable  in  feet. 
Then—K:X::D:D' 

Hence  X,  the  absolute  capacity  =— w- 

L  feet  : — — -  : :  5,280  feet,  or  1  mile  :  X  capacity  per  mile 

Hence  capacity  per  mi\e=^^^^^'-^^ 
^       ^  ^  DXL 

In  order  to  prevent  the  E.  M.  F.  of  the  battery  from  changing  in  case  of  a 
test  being  made  when  the  leading  wires  were  accidentally  crossed  or  the  cable 
grounded,  the  cable  or  condenser  is  normally  charged  through  the  A  megohm 
box,  but,  if  desirable,  said  resistance  can  l)e  cut  out  of  circuit  by  inserting  a  plug 
in  the  hole  marked  tV  megohm.  This,  however,  is  not  recommended,  as  expe- 
rience shows  thnt  on  short  cables  it  has  little  or  no  etTect.  However,  in  meas- 
uring the  capacity  of  long  cables,  the  ttj  megohm  should  l)e  removed,  as  it 
has  a  retarding  elTect  on  the  charge  and  ilischarge  of  the  comparatively  large 
current  involved. 

NOTES    ox    CAPACrrV     MKASTREMENTS    FROM     STANDARD    UNDERGROXTxi)     CABLE    CO.'s 
HANDBOOK   NO.   XVI.I,    1900. 

With  telephone  cables  there  are  two  methods  of  making  the  connection  ior 
tests  of  electrostatic  capacity : 

(1)  The  regular  or  old  trade  standard  method  of  testing  to  ground,  with  the 
connections  made  in  the  same  maimer  as  for  a  test  of  insulation  resistance, 
namely,  one  wire  against  the  remaining  wires  grounded  to  the  sheath. 

(2)  An  entirely  different  test  for  mutual  electrostatic  capacit.v,  in  which  one 
wire  is  measured  against  its  mate,  the  remaining  wires  being  grounded  to  the 
sheath. 

The  electrostatic  capacity  by  the  last  method  of  connections  is  the  least,  being 
about  two-thirds  the  capacity  by  the  former  method  of  connections. 

The  use  of  the  shunt  has  already  been  thoroughly  explained,  and  if  neces- 
sary can  be  used  in  this  work,  but  for  very  accurate  determinations,  unless  it  is 
calibrated  especially  for  capacity  tests,  it  can  not  be  relied  upon,  because  the 
self-induction  of  the  shunt  does  not  generally  bear  the  right  relation  to  the 
self-induction  of  the  galvanometer,  so  that  the  sudden  discharge  current  will 
not  divide  in  both  circuits  in  the  same  ratio  that  it  would  for  steady  currents. 
If  the  condenser  capacity  is  limited  so  that  it  can  not  be  made  comparatively 
near  the  capacity  of  the  cable,  good  results  can  be  obtained  by  subdividing  the 
battery  for  whichever  has  the  largest  capacity.     For  instance,  let  us  suppose 

(48?.) 


48 


Signal  Corps  Manual  No.  3. — Chapter  1 1 , 


that  the  condenser  has  four  times  the  capacity  of  the  cable,  then  we  sliouUT 
divide  the  l)atter.v  into  about  four  equal  parts  and  take  the  discharjie  detlection 
t>f  the  condenser  for  each  of  these,  use  the  sum  of  the  above,  which  rei)resents 
the  discharge  deflection  that  would  have  been  obtained  had  the  full  battery 
been  used  and  were  the  galvanometer  scale  long  enough  to  read  the  detlection. 
The  full  battery  should  then  be  used  to  obtain  the  discharge  detlection  of  the 
cable.     If  the  cable  has  the  larger  capacity,  the  operation  should  be  reversed. 

MEASUREMENTS    OF    INSULATION    RESISTANCE. 

In  making  the  measurements  of  insulation  resistance  a  reflecting  galvanom- 
eter can  be  used  by  connecting  it  to  the  posts  marked  Ga  (tigs.  ll-30.and  11-31) 
and  disconnecting  the  flexible  leads  adjacent  thereto  which  run  to  the  horizontal 
galvanometer,  or  when  approximate  tests  have  to  be  made  the  galvanometer  of 
the  set  can  be  employed  by  connecting  the  above-mentioned  flexible  leads  to 
the  post  marked  Ga.  In  like  manner  an  auxiliary  battery  can  be  connected 
to  the  posts  marked  Ba,  or  the  battery  of  the  testing  set  can  be  employed  by 
connecting  the  number  of  cells  required  to  the  flexible  cords  adjacent  to  Ba. 
Use  small  battery  at  first  and  gradually  increase  it  until  a  suitable  detlection  is 
obtained.    After  making  the  connections  indicated  above  the  handles  of  the  two 


SIMPLIFIE.D  INSULATION   RESISTANCE  DIAGFIAM 


SIMPLIFIED  DIAGRAM 
OFTHE  FISHER  TESTING  SET 

FOR  CAPACITY  AND  INSULATION  TEISTS 

Fig.  11-33.— LONG   SUBMARINE  CABLES.  TESTING,   MEASURING   INSULATION    RESIST- 
ANCE,  SIMPLIFIED     DIAGRAMS. 

(484) 


Long  Submarine  Cables,  Telegraphy,  and  Tests. — Chapter  11.  40 

double-pole  double-throw  switche,s  are  placed  in  the  direction  of  tlie  letters  "  C 
or  /  ".  The  two  leadinj?  wires  from  the  cable  conductor  and  from  the  ground  are 
connected  to  "  cable  posts."  Insert  plugs  into  the  two  holes  marked  /  and  .see 
that  no  plugs  are  inserted  in  the  holes  inarkeil  C,  (J,  and  //.  The  test  can  now 
be  niaile  in  the  ordinary  manner,  as  follows : 

Close  the  battery  circuit  by  means  <»f  the  key  Ba  and  its  accompanying 
holding-down  cam.  Shortly  before  the  period  of  electrification,  which  is  gen- 
erally one  minute,  has  elapsed,  press  down  the  key  marked  Ga  to  remove  the 
short  circuit  from  the  galvanometer,  when  tlie  ('.ellcction  can  be  read.  Tlicn  dis- 
connect the  leading  wires  from  the  cable  conductor  and  in  like  manner  measure 
the  deflection  due  to  the  leading  wires,  which  must  be  subtracted  from  the 
observed  deflection  first  read  to  give  the  true  deflection  due  to  the  cable. 

At  first  use  j^Vs  shunt,  gradually  decreasing  the  shunt  to  1. 

In  taking  the  constant  with  Fisher's  set  the  presumption  is  that  the  same  num- 
ber of  cells  is  used  both  in  taking  the  constant  and  in  measuring  the  unknown 
insulation;  consequently  tiie  number  of  cells  is  not  considered  in  the  formula. 
Where  it  is  necessary  to  vary  the  number  of  cells,  the  voltage  in  each  case  must 
be  taken  into  consideration.  This  is  thoroughly  explained  in  chapter  4  of 
this  manual. 

The  insulation  constant  of  the  galvanometer  is  next  determined,  as  follows: 

The  deflection  is  taken  through  100,000  ohms  or  yV  of  a  megohm,  therefore  remove 
the  plug  from  the  hole  marked  x'cr  megohm  and  insert  a  plug  at  G.  Use  whate^  er 
shunt  will  give  the  best  readable  deflection,  which  we  will  call  D.  Then  the  insula- 
tion constant  of  galvanometer =—- t=G 

lOXshuntused 

G=Galvanometer  constant,  or  deflection  through  1  megohm. 
Z)= Deflection  through  t^s  meghom. 
il/=Multiplying  power  of  shunt. 
Large  deflection  :  Small  deflection  :    :  Large  resistance :  Small  resistance. 
DXM  :  G  :    :        1  megohm       :       its  megolim. 

G=DXMX^. 
Let  /)'=Deflection  due  to  the  cable. 
L  =  Length  of  cable  in  feet. 

Q 

Absolute  insulation  resistance  of  the  cable=^— -— ^. 

For:  Large  resistance :  Small  resistance  :  :  Large  deflection :  Small  deflection. 

Absolute  resistance  :      1  megohm        :  :  G  :  D''XM. 

If   absolute    resistance    is    less    than    1    megohm,    the    words    "  Large "    and 
"  Small  "  in  above  proportion  should  be  reversed. 
Insulation  inverse  to  distance — 
Large  distance  :  Small  distance  : :  Large  per  mile  :  Small  absolute 

insulation  insulation 

Q 

L  feet  :  5,280  feet  ::  per  mile  insulation  :   jyj^ 

GL 

Insulation  per  mile=-- — — — — — — 

^  Z>XJ/X5,280 

It  is  best  to  make  the  regular  insulation  resistance  test  with  the  i^ 
megohm  in  series,  and  this  is  done  by  removing  the  plug  from  the  hole 
marked  ^  luegohm.  This  is  advised  so  that  the  battery  can  never  be  short- 
circuited.  Where  great  accuracy  is  desired  the  t^  megohm  can  be  subtracted 
from  the  calculated  absolute  insulation  resistance  to  get  the  true  insulation 
resistance. 

(485 » 


50 


Signal  Corps  Manual  No.  3. — Chapter  1 1 . 


MEASITJEMENTS   OF   CONDUCTOR   RESISTANCE. 

Place  the  handles  of  the  two  douhle-pole  douhle-throw  switches  in  the  dii-ec- 
tiou  "R  or  M  or  V  ",  figure  11-31,  insert  a  plug  in  the  hole  marked  R,  and  at  the 
same  time  see  that  no  plugs  are  in  the  holes  marked  M  or  V.  It  will  be  noted 
that  there  are  four  resistances,  viz,  1,  10,  100,  1,000  ohms.  Any  one  of  these  can 
be  used  in  the  test  by  removing  its  corresponding  plug  and  inserting  plugs  in 
llie  other  three  holes.  Before  connuencing  the  test  a  resistance  near  to  the 
probable  resistiince  to  be  measui-ed  should  be  loft  unplugged.  For  instance, 
if  5  oluns  or  less  have  to  be  measured  the  1  ohiii  resistance  sliould  be  left 


GCNEIRAL    SIMPLIFIED   DIAGPAM   FOR    FPCSlSTANCE    MCASURCMENT 
L 


R=lcrlOotlOOorlOOO 


Simplified  Diagram  of   the  Fishef-S  Testing   Set 

for  Resistance,    Murray  Loop  and  Varley    Loop  Testj 


>■  10  Coils  of  fOOu  •oth  -  looo  • 
10  Coils  o/aou  eoch-soo. 
*■>■  to  Coi  Is  of  IfrM  •och  -  160  ». 

Fl?;.  11-34.— LONG     SUBMARINE    CABLES,    TESTING,     COPPER     RESISTANCE,     MURRAY 
AND    VARLEY     LOOP,    SIMPLIFIED    DIAGRAM. 

unplugged.  If  lilt'  jirobablc  icsislaiicc  In  lu'  iiu'usiircd  lies  l)elwoen  .'">  and  HO 
olims  the  10  oiinis  resistance  siioidd  l)e  h'ft  uiiphigged  ;  if  tlie  resislance  to 
be  measured  is  over  ilO  ohms  the  100  (»hms  resistance  sliouid  be  left  unplugged. 
(!<iniiect  in  Ihe  resistance  in  be  measured  to  the  posts  L  and  A'.  By  means 
nf  liic  licxiide  cords  opimsitc  llic  posts  marked  ftii  connect  a  few  cells  of 
biillcry  al   lirsl,  and  if  necessary  tlic  wlmlc  IL*  cells  latei-.     ('onnect  tlie  llexible 

(48(!) 


Long  Submarine  Cables,  Telegraphy,  and  Tests. — Chapter  1  1 , 


cords  opitosile  llie  itosts  nmrketl  (la  lo  said  posts.  For  tlie  coniiuencement  of 
the  test  use  Tiym!   shmit,  decreasinj?  shunt  by  steps  to  1. 

The  test  can  now  be  made  by  first  placing  the  arms  of  the  "  Tens "  and 
"  Units "  dials  at  zero  and  moving  the  "  Hundreds  "  dial  to  J.  Press  down 
tirst  the  battery  key  and  instantly  thereafter  the  galvanometer  key,  and  note 
tlie  direction  in  which  the  galvanometer  pointer  moves.  If  the  battery  flexi])l(' 
cords  have  been  connected  as  indicated  by  the  corresponding  plus  and  niiiuis 
signs,  a  deflection  of  the  galvanometer  toward  the  plus  sign  indicates  that 
the  dial  i-esistance  must  be  increased,  while  if  the  deflection  is  in  the  opposite 
direction,  the  dial  resistance  must  be  decrea.sed.  With  this  information  in 
mind  an  instant  only  is  required  to  determine  between  which  two  sets  of 
"  Hundreds  "  the  balance  point  lies.  Having  found  this,  place  the  pointer  at 
the  lowest  of  the  two,  and  in  like  manner  determine  between  which  two  sets  of 
"  Tens  "  the  balance  point  lies,  placing  the  switch  at  the  lowest  of  these.  The 
final  balance  can  then  be  found  by  rotating  the  "  Units  "  switch  until  a  point  is 
i-eached  when  there  is  no  deflection  of  the  galvanometer.  With  the  "  Tens  " 
and  "Hundreds"  switches  the  reading  is  tid<en  between  the  two  contact  arms, 
while  with  the  "  Units "  switch  the  reading  is  taken  at  the  segment  with 
which  the  rotating  arms  is  in  contact. 

Note. — In  using  Fisher's  Set,  for  Resistances,  or  Murray  &;  Varely  loop  test, 
it  is  always  best  to  keep  the  simplified  diagram  before  the  tester's  eyes,  as  it 
facilitates  thorough  understanding.  This  diagram  can  be  roughly  drawn  in  less 
than  one  minute. 


B=IOOO-A 

R  =  l,  10.  lOOorlOOO 

Letting  R  =  the  implugged  resi-stance  to  the  right  of  the  double  switches. 
I-etting  A  =  the  reading  of  the  dial  switches  arranged  in  the  order  of 
hundreds,    tens,   units, 

A:X ..1,000— A.R :.X=-^--^^  -    ohms  the  resistance  to  be  measured. 
1,000— J. 

Tlic  value  of  tlie  teiui       J     -    can  be  found  in  the  aceompaiiyiiig  table,  when  it 
is  only  necessary  to  multiply  said  value  by  t'.ie  amount  of  resistance  unplugged. 


iirUUAY    LOOP    MKTHOI)   OF    LOCATING    CKOr.NDKD    OK    IHOSSKI)    WlKKS. 

This  is  the  simplest  method  of  locating  grounds  or  crosses,  and  is  cliierly 
applicable  when  the  faulty  and  good  wire  are  of  the  same  size  and  length; 
hence  it  can  be  used  to  locate  such  faults  In  telephone  and  telegraph  cables 
where  all  the  conductors  seldom  become  faulty  before  the  method  can  be  applied. 
It  can  also  be  used  in  the  case  of  an  electric  cable  where  the  outgoing  and 
incoming  cable  are  the  same  size  and  length  and  where  one  of  them  is  not 
faulty.  To  apply  this  method,  join  the  faulty  and  good  conductor  at  the  distant 
end  of  the  cable  and  connect  the  faulty  conductor  to  L  and  the  good  conductor 
to  K.  Place  the  two  double-throw  doul)le-pole  switches  in  the  direction  of  "R  or 
21  or  V  ",  insert  plugs  in  the  two  holes  marked  J/,  and  be  sure  that  no  plugs 


i4S7) 


52 


Signal  Corps  Manual  No.  3. — Chapter  1  1 . 


are  in  the  two  holes  marked,  respectively,  V  and  R.  The  resistances  1,  10,  and 
100  can  be  either  plugged  or  unpluggetl  without  affecting  the  test.  Connect  the 
ground,  or  in  the  case  of  a  cross  the  wire  crossed  with  the  ono  used  in  the 
test,  to  the  post  marked  Gr.  The  galvanometer  and  battery  are  connected  in 
the  same  manner  described  under  "  Measurements  of  conductor  resistance." 
The  description  there  giving  the  operating  of  dial  switches  is  exactly  the  same 
as  must  be  followed  in  this  case. 


B  =  lOOO-A 


Part :  WTiole : :  Part :  Whole 


yl:  1,000 


A' :         L  or  whole  loop .".  X=- 


4Il 

.000 


Letting  .4  =  the  reading  of  the  dials  which  gives  a  balance  of  the  galvanom- 
eter. 
2v=the  total  length  of  the  circuit=twice  the  length  of  the  cable 
if  the  good  and  bad  wires  are  in  the  same  cable.  The 
length  can  be  in  inches,  feet,  yards,  miles,  or  ohms,  and  X, 
the  result,  will  be  in  the  denomination  used. 


Then, 


The  distance  to  the  fault  from  the  post  L= 


AXL 
1000" 


The  check  method  can  now  be  applied  by  connecting  the  faulty  conductor  to 

^and  the  good  conductor  to  L. 
Letting  J.^=  the  reading  of  the  dials,  which  gives  a  balance.  1,000  — J.'  should 

=A,   which  substitute    in    the    above    equation    for    A,    which    gives 

—         —  X  L  the  distance  to  the  fault  by  the  check  method,  which 
1000  ^ 

should  be  the  same  as  before. 

Another  mctliod  of  cliecking  the  accuracy  of  thc^  rc'sult  is  lliat  in  every  case 
.1.1'  siiould  e(|ual  1.000. 

When  dealing  witli  faulls  of  higii  resistance,  .lO  or  more  ci'lls  of  battery 
iiiiiy  have  to  he  us(>(I.  The  l)a(tery  should  be  connected  to  the  posts  Bo,  and 
the  corresponding  llexilile  cords  sliould  be  disconnected  from  the  battery  of 
the  set. 

Tlie  Murray  looji  may  lie  used  where  the  two  wires  conslituling  (he  loop 
are  of  different  kinds  and  resistances.  First  measure  resistance  of  looj),  then 
take  a  Murray  loop  test,  when  .V  will  be  found  in  ohms;  convert  .V  into  dis- 
tance by  reference  to  wire  tables. 

VARI.KY    I.OOI'    MKTIIOI)    OK     I.OCATINC     CatOt'NDEI)    OR    CUOSSKn     WIKKS. 

Tlie  Murray  loop  irietlmd  Is  jireferable  to  the  Varley  loo))  nielho<l  with  the 
Fisher's  set,  for  with  tlie  Murray  loop  no  e.xlra  resistance  If  is  added,  nor  is 
it  re<piired ;  while  the  Varley  looj)  test  calls  for  extra  resistance  A'  and  its 
elimination,   with   no  increase  in  edicMMicy  to  roiiip(>nsate  for  the  extra  labor. 

(488) 


I 


Long  Submarine  Cables,  Telegraphy,  and  Tests. — Chapter  II.  53 

Join  the  faulty  and  jiond  condurtor  at  the  distant  end  of  the  cahle,  and  at 
the  near  end  of  tiie  calile  connect  the  former  to  the  post  marked  L  and  tlie 
latter  to  the  post  marked  K.  Then  measure  the  resistance  of  the  circuit  as 
described  under  "  Measurements  of  conductor  resistance." 

Let  r=said  resistance. 

Place  the  handles  of  the  two  double-throw  double-pole  switches  in  the  direc- 
tion of  "iiJ  or  .17  or  V  ".  Insert  plui^s  in  the  two  holes  marked  V,  and  see  that  no 
plugs  are  in  the  two  holes  marked,  respectively,  M  and  R.  Join  the  faulty  and 
good  wires  at  the  distant  end  of  the  cable  and  connect  the  former  to  L  and 
the  latter  to  K ;  connect  the  ground  or,  in  the  case  of  a  cross,  the  wire  crossed 
with  the  one  used  in  the  test,  to  the  post  marked  Gr ;  unplug  the  resistance 
marked  100  and  plug  the  resistance  marked  1  and  10,  connect  the  battery  and 
galvanometer  and  operate  the  dial  switches  in  the  same  manner  described 
under  "  Measurements  of  conductor  resistance."  If  the  balance  can  not 
readily  be  obtained,  it  may  be  necessary  to  unplug  the  10-ohni  or  perhaps  the 
1-ohm ;  the  other  two  resistances  must,  of  course,  be  plugged.  The  dial 
switches  are  now  operated,  as  described  under  "Measurements  of  conductor 
resistance,"  until  a  balance  is  obtained,  when  the  reading  is  I'ecorded. 


B  =  IOOO-A 


Let  R—the  resistance  unplugged  in  the  rheostat, 
Let  r=the  resistance  of  the  faulty  and  good  wires, 

Lfet  A=the  reading  of  the  dials  which  gives  a  balance  of  the  galvanometer, 
and. 

Let  5  =  1.000—1, 

Let  a=the  resistance  to  the  fault  from  L, 

A :1, 000 ::  a  ohms: r+ E(o]\m^).-  A  .000(1= ArXAr.\a=^^^'^^:^  ohms 

1,000 

CHECK    MKTHOl). 

Connect  now  the  faulty  wire  to  A'  and  the  good  wire  to  L,  and  proceed  in  flic 
same  manner  to  timl  the  new  values  ^1,  B,  A",  and  a,  which  for  the  check  method 
we  will  call  A',  B',  A',  and  a'. 


B'=IOOO-A'      '-^"'^ 


(489) 


54  Signal  Corps  Manual  No.  3. — Chapter   11. 

The  resistance  to  the  fault  from ; 

B':1.000::(R'-\-a'):iR'+r) 

l,000a'+l,000R'=B'Ji'+B'r:.1.000a'=B'r+B'R'-l,000R' 
As  B'=l.OOO-A'  substitute  it  for  B' 
Hence:  1.000a'=jB'r+l,000i?^-^^i?^-l,000A'^ 

D/   4^  R^ 

a'=  ~ — -  ohms.     Answer,  which  should  be  the  same  as  found  iox  "a"  above. 

1,000 

Let  ?)  =  the  resistance  of  tlie  faulty  \vire=one.-halC  the  resistance  of  the  loop 
where  good  and  bad  wires  are  of  the  same  size  and  are  in  one  cable. 

Let  L=the  length  of  cable. 

Then, 
a  ohms  as  found  above  :  b  ohms  : :  A',  the  distance  to  the  fault  by  first  method  :  L 
Hence — 

a'  ohms  as  found  above  :  b  ohms  : :  X  the  distance  to  the  fault  by  check  method  :  L 

Hence:  X=^;—  which  should  equal  ^— 
b  0 

a  ohms  should  equal  a'  ohms. 

ARRANGEMENT    OF    TESTII^JG    SET. 

The  convenient  arrangement  of  the  testing  set  at  the  cable  office  is  of  great 
importance.  Not  only  does  this  make  tests  easy,  but  it  tends  to  accuracy  as 
well,  since  troubles  are  easily  traced  in  sets  where  the  wiring  is  well  laid 
out  and  all  parts  of  instruments  easy  of  access. 

The  wiring  should  invariably  be  done  with  best  rubber-covered  wire  or,  better, 
cable  core,  supported  on  porcelain  cleats  or  knobs.  The  layout  of  the  instru- 
ments on  the  table  is  shown  in  figure  11-8.").  Tlie  galvanometer  should  be  on  a 
.separate  shelf  not  connected  with  the  table.  It  should  be  about  the  height  of 
the  shoulder  from  the  floor.  On  the  opposite  end  of  the  table  the  lamp  and 
scale  are  supported  at  the  same  height  on  a  shelf  or  stand  separate  from  the 
table.  By  this  arrangement  of  the  galvanometer,  lamp,  and  scale,  the  scale  is 
in  full  view  while  the  Wheatstone  bridges  or  keys  are  being  manipulated. 

The  galvanometer  lamp  is  usually  an  electric  lamp,  with  a  straight  filament, 
placed  behind  the  slit  in  the  scale,  and  the  concave  galvanometer  mirror  rotU'cts 
an  imag(;  of  the  filament  as  a  brilliant  vertical  line  on  the  scale,  when  the  scale 
and  galvanimieter  are  the  proper  distance  aiiart  for  correct  focusing.  If  electric 
light  is  not  available,  an  oil  lamp  may  be  used. 

EXCESSIVE    E.    M.    V.    NOT    TO    HE    I'SEO. 

After  a  vnhlo  is  laid,  the  E.  M.  V.  used  in  testing  sho\dd  not  exceed  40  volts, 
ex(«>pt  when  necessary  to  obtain  the  recpiired  current  in  IcK'ating  breaks,  when 
a  rea.sonable  increased  voltage  may  be  u.sed,  but  should  be  applied  to  the  cable 
the  shortest  time  i)ossible  to  obtain  desired  results. 


(400) 


Long  Submarine  Cables,  Telegraphy,  and  Tests.— Chapter  11.  55 


46581°— 17- 


(491) 


56 


Signal  Corps  Manual  No.  3. — Chapter  1 1. 


The  resistance  box.  adjustable  from  2  to  11,220  ohms,  sliowu  in  tisure  11-35, 
is  used  in  the  battery  circuit  when  making  bridge  measurements,  and  readily 
permits  adjustment  to  the  proper  current  strength  as  shown  on  the  milli- 
ammeter. 

For  locating  high  resistance  leaks,  when  sufficient  variation  of  the  current 
by  using  reasonable  voltage  can  not  be  obtained,  recourse  must  be  had  to 
Clark's  potential  test,  or  Jordan  &  Schonau's  modification  of  the  earth  overlap 
test  appearing  later  in  this  chapter. 


©BINDING  POST 


1666661 


^ AFTER 
3TAN>\^ 


OOQ 


O 

o 
o 
o 

o 


F?ESISTANCE 

i-k>vwvvO 


GROUND  (^ArE 


'fJote-Connections  from  binding  posts  otsparkinqset 
to  cable  are  made  by  flexible  ivires  wth  tnps 
on  the  ends,  via  the  bow  leads 


REICORDER" 


Q 


r^ 


rO 


Pi 


|i|i|i|*U 


DIAGRAM    or    SPEAKING    CONNECTIONS,  U.S. A.T.    BURNSIDE. 


^  C-S»  DATA 

/     \  I*    \    Camtantpluiittt'roijIiibanjnrcoffatjhayKjii'^  Ruri7, 


MUaTJMUAx] 


^^^Jfff!lJ^Z^t::^^ 


Fig.  11-36.— LONG    SUBMARINE   CABLES,   TESTING.   TEST    ROOM    CONNECTIONS,    U.   S. 

A.   T.    BURNSIDE. 

(jarc  iiuist  be  taken  in  11h>  insulation  t(>st  not  to  dopross  short-circuit  key  until 
cable  has  been  charged  U>v  It)  or  l."i  seconds. 

To  get  capacity  indications  on  gMlvanometer  the  amount  of  "throw"  of 
galvanometer  on  oi»eidng  or  closing  nncrsing  key  irit]i  the  Hhort-circuit 
key  (hprcHHcil  will  give  the  capacity,  i)rovided  the  amoinit  of  this  tlirow  is 
compared  witii  that  given  by  a  condenser  of  known  capacity  connected  in 
place  of  line  and  earth,   when   l>;ittei\v   and   sliiinl    ai'e   Ihe  same   in   both   ca.sc's. 

(492) 


Long  Submarine  Cables,  Telegraphy,  and  Tests. — Chapter  11.  57 

It  imisl  he  understood  that  tliis  method  gives  reliuhle  indiralions  only  with 
comparatively  short  cables.  For  long  cables  Gott's  test,  described  at  length 
in  the  books  of  reference,  should  be  employed. 

In  all  measurements  let  the  rule  be  to  begin  with  a  large  shunt  and  small 
battery,  gradually  increasing  the  battery  and  gradually  decreasing  the  shunt. 
This  method  will  prevent  damage  to  the  instrument. 

LOCATION    OF   FAULTS    IN    SIIJMAKINK    CABLES. 

The  application  of  the  measurements  just  described  in  the  local i<)?i  of  faults 
may  now  be  dealt  with.  The  more  complete  exposition  of  the  subject  in  the 
books  of  reference  cited  is  recommended  to  those  wlio  desire  to  go  into  the 
matter  more  deeply. 

Faults  on  cables  are  similar  in  iiattirc  to  llmsc  on  land  lines.  AN'licii  tli(> 
cable  is  comi)letely  I'uptured  faults  may  be  dcscrilu'd  under  the  folUjwing 
headings  of  Chuss  I : 

Class  I:  First.  The  conductor  is  in  coiitacl  witii  liie  metal  slu^athiiig  and  is 
"  dead  grounded." 

Second.  The  conductor  is  considerably  exposed  hy  nnicli  ot"  the  insulation  at 
and  near  the  end  being  broken  away. 

Third.  When  the  end  of  the  conductor  is  only  partially  exposed  or  deeply 
buried  in  nuid  and  sand. 

Fourth.  AN'hen  the  insulating  material  is  di-awri  well  oxer  the  broken  end  of 
the  c<»ndi:ctor  almost  completely  insidating  it. 

Class  II:  Conductor  ru])tured  ;  insulation  remainiui;  iiitacl. 

Class  III:  Break  or  abrasion  of  the  insulating  mateiial.  causing  either  a 
high-resistance  leak  (escape)  or  one  approximating  to  a  "dead  ground,"  de- 
l»ending  upon  the  amoiuit  of  exposure  of  the  conductor. 

The  behavior  of  the  fault  inider  working  conditions  oi;  test  will  usually  de- 
termine to  which  class  it  belongs. 

Rupture  of  the  cable  is  attended,  of  course,  with  total  cessation  of  signals 
fnmi  the  distant  end,  and  this  iisually  occurs  su<ldeidy.  The  end  of  the  con- 
ductor is  generally  left  more  or  less  exposed.  If  left  much  exi)osed,  or  grounded 
on  the  cable  armor,  the  galvanometer  will  indicate  a  comparatively  steady  cur- 
rent when  moderate  battery  power  is  applied.  If  the  exposure  is  small,  or  the 
end  is  buried  in  mud,  great  fluctuations  in  tlie  current  will  be  produced,  and 
greatly  different  when  different  ends  of  the  battery  are  placed  to  line.  If  the 
conductor  is  well  drawn  back  into  the  insulation,  or  the  conductor  is  ruptured 
inside  the  insulating  covering,  of  course  notliing  but  the  transitory  current  of 
charge  and  discharge  will  be  observed. 

Damage  to  the  insulation,  exposing  more  or  less  of  the  conductor,  very 
frequently  is  first  noted  as  a  "leak,"  which  bi'comes  worse  and  worse,  until 
connnunication  is  interrupted.  Unless  the  damage  is  extensive,  the  reception 
of  feeble  signals  from  the  distant  station  will  disclose  that  the  fault  belongs 
to  Class  III  and  that  the  cable  is  not  ruptured. 

In  locaing  the  first  of  Class  I  it  is  evident  that  it  requires  only  the  measure- 
ment of  the  copper  resistance.  This  divided  by  the  resistance  per  mile  will 
locate  the  fault.  In  No.  4  of  Class  I  and  in  Class  II  a  measurement  of  capacity 
is  required.    This  divided  by  capacity  per  mile  gives  the  distance. 

In  all  the  others  where  partial  exposure  of  the  conductor  is  involved  and 
only  one  end  is  available  at  the  testiug  room,  localization  is  difficult,  owing  to 
the  polarization  at  the  fault  and  its  consequent  change  of  resistance  with  dif- 
ferent sti-engths  and  directions  of  current,    \\hea  faults  are  minute  this  polari- 

(493) 


58 


Signal  Corps  Manual  No.  3. — Chapter  1 1, 


zation  changes  resistances  from  a  few  ohms  to  thousands,  and  vice  versa,  with 
such  rapidity  as  to  require  the  greatest  sliill  and  judgment  in  testing.  In 
general,  by  putting  zinc  to  line,  the  generation  of  hydrogen  and  consequent 
cleansing  from  metallic  salts  at  the  fault  tends  to  open  it  up ;  while  putting 
carbon  or  copper  to  line,  by  coating  the  fault  with  chloride  of  copper,  will  cause 
the  resistance  to  rise  by  sealing  up  the  fault. 

If  the  defect  in  insulation  is  small  it  is  sometimes  difficult  to  detect  which 
pole  causes  the  most  rapid  polarization. 

When  the  cable  is  coiled  in  the  tanks,  where  both  ends  are  available,  or  when 
two  cables  have  been  laid  between  two  points  permitting  their  looping  at  the 
far  end,  or  when  the  cable  has  multiple  cores  one  or  more  of  which  remain 
uninjured,  faults  in  the  insulation  of  a  cable,  where  the  conductor  is  not  broken, 
may  be  quite  accurately  and  easily  located  by  the  "  loop  test."  This  being  the 
simplest  method  of  locating  these  faults  in  cable,  it  will  be  dealt  with  first. 

First  measure  the  resistance  of  the  loop  which  we  will  call  Tj  with  the  two 
ends  of  the  conductor  connected  to  the  Wheatstone  bridge.  Then  change  the 
connection,  as  shown  in  figure  11-37. 


fl I  I  I  I  I  I 


m  -  16  used  to  tahe  copper  resistance  of'  the  loop, 
g  -   is  used  to  balance  for  the  loop  lust  ^hen  one 
IS  used  the  other  is  not  used. 

Fig.  11_37._LONG    SUBMARINE    CABLES,    TESTING,    LOCATION    OF    GROUND, 
LOOP    TEST,  CONNECTIONS. 


SIMPLE 


It  will  be  noted  that  the  end  with  small  resistance  between  it  and  the  fault  Y 
must  i»e  connected  with  A',  otherwise  no  balance  can  be  obtained.  When  this  is 
found  to  be  the  case  transpose  the  ends.  When  balance  is  obtained  call  the 
values  in  balance  arms  a  and  h  and  anu)unt  unplugged  in  resistance  R,  as  noted 
in  diagram. 

a  :  «  +  />  ::  A''  :  L-\-R  or  Tart  :  Whole;  "  !t*arf  :  AMiole,  which  is  similar  to  the  loop 
proportiona  for  the  Fisher's  set  previously  shown, 


(404) 


Lx)ng  Submarine  Cables,  Telegraphy,  and  Tests. — Chapter   11.  HP 

Hence — 

a+b 
Wlien— 

a=b  we  have  X=«(^+^)  or  X=ldrli 
2a  2 

To  find  the  value  of    Y,  use  this  proportion,  i.e., 
6:  b+a  ::  Y+R:  L+R 
or  Part  :\\liole::   Part  :\\liole 
Hence — 

b  Y+bR+a  Y+aR=bL+bR 

Y{(i+b)=bL+bR-aR-bR:  -bR  and  +bR  canca], 
Then— 

Y{a-\-b)=bL-aR -Mid   Y=^^~^^ 
a  -\-  b 

Wlien— 

a=b,  then  Y=a  ^^~^^  hence  Y=^~^ 
2a  2 

A  simple  inspection  of  the  preceding  diagram  show.s  these  formulae  to  be 
correct. 

Wlien  tlie  break  is  of  tlie  .second  or  tliird  Ivind,  under  Class  I,  it  is  usually 
indicated  by  more  or  less  rapid  polarization  wlien  the  copper  or  carbon  pole 
is  put  to  line ;  that  is,  by  a  rise  of  resistance.  The  fact  that  it  is  a  break  is 
indicated  by  the  cessation  of  even  feeble  signals  from  tlie  distant  station. 
Sudden  variations  or  jumps  of  resistance  when  the  battery  is  applied  indicates 
that  the  conductor  is  only  partially  exposed,  or  that  it  is  deeply  buried  in  mud 
or  sand,  thus  preventing  free  escape  of  the  gases  liberated  by  electrolysis. 

One  of  the  successful  methods  of  testing  through  tlie  exposed  end  of  the 
conductor  at  a  total  break  and  obtaining  the  copper  resistance  up  to  the  break 
is  that  devised  by  Prof.  Kennelly.  This  method  of  eliminating  the  resistance 
of  the  exposed  end  itself  depends  upon  the  fact  that  the  resistance  of  the  fault 
varies  inversely  as  the  square  root  of  the  current  strength  passing  through  it, 
provided  the  exposure  is  not  less  than  half  of  a  square  centimeter. 

Supposing  the  current  througli  the  break  be  increased  four  times,  the  apparent 
resistance  will  be  decreased  one-half,  for  V4=2  and  inversely  is  1/2.  The 
strength  of  the  current  should  in  no  case,  however,  exceed  25  milliamperes. 
The  measurements  should  be  made  by  the  false  zero  metliod,  using  zinc  (nega- 
tive current)  to  line. 

The  usual  arrangement  of  the  Wheatstone  bridge  for  copper  resistance  is 
made.     See  simplitied  diagram  for  conductor  resistance  measurements,  figure 
11-38,  and  diagram  of  test  sets  at  cable  ofhces,  Washington-Alaska  system,  tigure 
11-35.     If  X  be  tlie  resistance  up  to  the  break,  A  the  resistance  obtained  by  meas- 
urement with,  say,  4  milliamperes,  B  with  IG  milliamperes  being  four  times  as 
many  as  with  A,  then,  using  Kennelly  two-current  false  zero  formula, 
Let  X=resistance  of  the  cable  to  the  break, 
Let  y'=resistance  of  tlie  fault. 
Then— 

A=X+Y, 

B=X+1/2T  (multiply  both  memliers  by  2). 


We  have- 


2B=2X-\-Y,  subtracting  first  equation. 

A=X+Y. 

2B — A^=X,  the  reistance  of  the  cable  to  the  break. 

(495) 


60 


Signal  Corps  Manual  No.  3. — Chapter  11. 


For  example,  if  the  measurement  with  4  milliamperes  gave  1.650  ohms,  and 
with  16  milliamperes  1,560  ohms,  the  resistance  up  to  the  break  is  1,560X2 — 
1.650=1,470  t)lims.  Greater  exactness  can  be  secured  by  taking  the  exact  ratio 
of  currents  going  to  line  by  inserting  a  milliammeter  between  the  bridge  and  the 
cable.  These  ratios  can  be  inserted  in  the  general  formuhx.  For  this  fornmla 
and  the  general  discussion  of  the  method,  reference  is  made  to  tlie  works  cited 
at  the  beginning  of  this  chapter. 


ig.  11-38.  — LONG    SUBMARINE    CABLES,    TESTING,    LOCATION    OF   GROUND,    PROFES- 
SOR   KENNELLY'S    METHOD,    COPPER     RESISTANCE    CONNECTIONS. 

Simplicity  is  a  large  factor  in  tlie  rapid  work  necessax\v  on  a  cable  sliip,  and 
it  has  been  found  by  experience  that  tests  based  on  a  variation  of  currents,  with 
resultant  effects  on  the  resistance  of  the  fault,  are  the  best.  The  Jona  curve 
is  based  on  variations  of  current ;  the  regularity  of  the  curve  shows  tlie  depend- 
ence to  be  placed  on  the  tests;  the  tests  have  the  advantage  of  scale  zero; 
besides,  data  are  furnished  for  solving  a  number  of  other  scale-zero  fornuilje  if  it 
is  .so  desired. 

Testing  in  a  jar  of  sea  water  on  a  desk,  with  every  advantage  and  no  earth 
currents,  will  show  how  difficult  it  is  to  locate  faults  with  absolute  accuracy. 

Ab.solutely  accurate  locations  of  faults  also  can  not  be  made  on  account  of  the 
following:  Errors  made  in  location  of  cabl(>  when  it  is  originally  laid  in  the  open 
sea  ;  didiculty  in  calculating  for  the  extra  slack  cable  i)ai<l  out  when  the  cable  is 
in  process  of  laying. 

In  general,  the  location  of  faults  of  Class  III  presents  the  greatest  diffi- 
culty. Of  course,  if  a  second  and  .sound  cable  or  another  sound  core  in  same 
cable  joining  the  two  places  is  available,  the  distant  ends  are  looited,  and 
the  reliable  "  h>op  test "  may  be  used. 

And  when  the  exposure  of  the  conductor  is  considerable,  making  the  fault 
resistance  so  low  that  not  any  or  barely  perceptible  signals  can  be  obtained 
from  the  distant  stiition,  .Tonsi  curve  and  forninl:r,  based  on  Jona  curve,  scale 
zi'i-d  diita  may  he  niijilicd,  tlic  distiiiit  end  being  insulated. 


(490) 


Long  Submarine  Cables,  Telegraphy,  and  Tests. — Chapter 


01 


No   other    very    sat isfju'tory    inetliod    exists   of   locating   leaks    (escapes)    on 
cables  when  facilities  exist  for  taking;  measurements  at  one  end  only. 


CLAUK  S     I'OTKNTIAr.    TEST. 


[Sep  Haines"  Manual.] 


This  depends  on  the  principle  that  in  any  circuit  with  resistance.s  in  series 
tlie  fall  of  potential  at  any  point  is  proportional  to  the  resistance  passed 
over,  befrinninj;  at,  the  hifih  potential  terminal.  The  instruments  required  at 
the  main  station  are  a  delicate  galvanometer,  high  resistance  Tip  to  1(X),OUO 
ohms,  a  Weston  voltmeter,  and  a  box  of  standard  coils.  The  Wheatstoiie 
bridge  will  answer  for  the  latter. 


Cable 


— <HjmmHUHnmuh 


HR 


Fig.  n-39.— LONG    SUBMARINE    CABLES,    TESTING,    LOCATION    OF    GROUND. 
CLARK'S    POTENTIAL    TEST,   CONNECTIONS. 

At  the  far  station  the  box  of  standard  coils  is  not  required.     However,  it 
is  better  for  each  to  be  the  main  station  in  turn  and  compare  results. 
The  comiections  at  the  main  station  are  as  shown  in  figure  11-39. 
The  connections  at  the  distant  station  are  as  shown  in  figure  11^0. 


Coble 


^ 


o 


HR 


1  T 


Fig.  11-40.— LONG    SUBMARINE   CABLES,    TESTING,    LOCATION    OF   GROUND,    CLARK'S 
POTENTIAL    TEST,   CONNECTIONS    AT    DISTANT    STATION. 

Before  closing  the  circuit  the  voltage  of  the  battery  B  is  determined  with 
the  Weston  voltmeter,  cell  by  cell,  so  the  low  reading  scale  may  be  used  and 
the  sum  of  these  voltages  taken.  ^C  is  the  box  of  standard  coils,  which  should 
be  at  first  unplugged  to  a  resistance  approximately  equal  to  one-half  that 
of  the  cable. 

The  galvanometer  G  and  high  resistance  ER  are  connected  in  series,  as  shown. 
The  number  of  cells  and  UR  should  be  proportioned  as  to  give  nearly  a  full  scale 

(497j 


62  Signal  Corps  Manual  No.  3.— Chapter  II. 

reading  when  the  galvanometer  is  connected  with  J..  First  take  a  reading  at  both 
stations  with  G  connected  ^^ith  A  and  line  open  at  C.  This  deflection  will  corre- 
spond to  the  total  battery  voltage  as  shown  by  the  sum  of  readings  of  the  voltmeter. 

Suppose  the  total  number  of  volts  is  P  and  the  deflection  is  D;  then  —  will  give  the 

number  of  divisions  of  the  scale  corresponding  to  one  volt. 

Now,  disconnect  batteries  and  connect  the  galvanometer.s  with  the  line  at 
each  station  and  observe  the  deflections  due  to  eartli  current  (E.  C),  both  in 
directiwi  and  amount. 

The  main  station  then  connects  battery,  standard  coils,  and  cable,  as  shown 
in  figure  11-39,  and,  having  arranged  time  with  distant  station,  they  talie  the 
following  readings,  as  nearly  together  as  possible: 

Main  station  takes  readings,  first,  with  G  connected  with  A,  and  then  with 
G  connected  with  C.  Distant  station  witli  switch  turned  to  C  simply  reads 
deflection  and  reports  it  to  main  station.    All  readings  are  reduced  to  volts. 

These  readings  are  designated  as  V,  v.  and  v',  respectively,  v  and  v'  are 
then  corrected  for  earth-current  readings,  adding  the  value  of  earth  current  if 
it  is  against  and  subtracting  if  it  is  nnth  the  battery  current. 

The  distant  station  then  sends  the  corrected  result  to  main  station.  The 
formula  for  the  solution  is  as  follows : 

a?=resistance  from  main  station  to  fault. 
■i?=number  of  ohms  unplugged  at  AC. 

R:V—r::X:v—v'. 

For  example,  suppose  the  total  voltage  of  battery  in  figure  11-39  were  11.2,  and 
that  the  galvanometer  through  the  high  resistance  gave  a  deflection  of  273,  then 

^= =24.4  scale  divisions  per  volt.     In  like  manner  distant  station  determines 

the  value  of  his  deflections.  Suppose  it  is  27  divisions  per  volt.  Earth  current  gives 
18  divisions  against  direction  of  testing  current  at  both  stations. 

Now,  suppose  V  is  265  divisions,  v  193  divisions,  and  v'  65  divisions. 

i2=800  ohms. 

These  would  correspond,  respectively,  to 

18 
-: — =.74  E.G.  volts  at  main  station 
24.4 

1  Q 

i^=.67  E.G.  volts  at  distant  station 
27 

|?^=10.9  volts  V 
24.4 

—=7.9  volts  V 
24.4 

—  =1.4  volts  v' 
27 

7.9+.74=8.64  corrected  v 
1.4-f  .67=2.07  corrected  v' 

Substituting  in  formula 

^^800(8.64-2^7)^5256^^3^,  ,,,^^^ 
10.9-8.64         2.26 

2325 

If  the  rcsiHtance  of  tlu;  cable  is  8.5  ohms  |)cr  nautical  mile,  the  fault  is  -——=273.5 

8.5 

tnilea  distant  from  main  station. 

(498) 


Long  Submarine  Cables,  Telegraphy,  and  Tests. — Chapter  11.  63 

More  accuracy  would  probably  be  reached  by  repeating  the  test,  using  a  -new 
value  of  R  approximating  to  x,  as  found  above. 

One  great  advantage  of  the  Clark  test  is  that,  as  readings  at  the  two  ends 
may  be  made  practically  simultaneously,  errors  due  to  irregular  polarization 
and  earth  currents  are  eliminated. 

EARTH    OVERLAP    TEST. 

Where  both  stations  are  equi]»iied  with  full  sets  of  instruments  one  of  the 
best  metho'ls  of  localizing  faults  due  to  defects  in  insulation  is  called  the  earth 
overlap  test.     It  is  particularly  applicable  to  high-resistance  faults. 

In  effect  the  measurements  are  made  with  a  view  to  determining  how  nmch 
resistance  should  be  put  in  at  the  station  nearest  to  the  fault  in  order  to 
make  the  resistances  on  each  side  of  the  fault  ccjual. 

A  y  X  B       r        C 


Fig.  11-41.— LONG    SUBMARINE    CABLES,    TESTING.     LOCATION    OF    GROUND,    EARTH 
OVERLAP    TEST,    DIAGRAMMATIC. 

The  measurements  are  made  by  the  observers  alternating  in  measuring  line 
resistance  with  distant  station  earthed,  each  allowing  a  specified  number  of 
minutes,  say  three,  for  each  station's  tests.  Both  should  measure  in  the  same 
way — that  is,  either  with  the  false  zero  with  zinc  to  line  or  with  reversals. 
Both  use  the  same  number  of  cells  testing  battery. 

Let  AB  be  a  cable  with  a  fault  in  it  at  z  (tig.  11-41).  Suppose  the  copper 
resistance  of  the  cable  when  sound  to  be  known  having  a  value,  L,  and  the 
fault  occurs  at  distance  x  from  B. 

If  tests  are  made  at  the  end  B,  it  is  evident  that  when  a  resistance  r  is  in- 
serted, making  a'+r=y,  then  the  following  equations  result: 

x-\-y=^L;  x-\-r=y 
y=L—x 

1        T  L—r 

:.oc-\-r=L  —  x;x=^—- 

L  —  r 

or  substitute  first  value  of  y  in  first  equation;  when  x-\-x-Tr=L :.2x=L  —  r;  3^=— .,    > 

same  as  before. 

The  routine  is  as  follows:  B  tests  first  and  gets,  say.  2.500  ohms,  then  .1 
gets  3,000  ohms.  They  exchange  results.  B  now  inserts  a  resistance  which 
should  be  greater  at  first  than  the  difference  between  the  results,  owing  to 
resistance  at  the  fault. 

For  example,  B  inserts  1,000  ohms  and  tests  three  minutes  with  .1  earthed. 
He  then  earths  through  the  inserted  resistance  for  three  minutes  and  -1  tests. 

They  then  compare  results,  the  last  at  B  and  first  at  A  being  considered 
most  reliable. 

B  now  gets  3.800  ohms  and  .1  3.500,  so  1.000  ohms  is  too  much.  B  inserts 
600,  800.  650.  7tK),  and  670  ohms  in  succession,  going  alternately  too  low  or  too 
high  until  at  670  both  B  and  .1  get  a  mean  result  practically  identical  or  about 
3,500  ohms. 

(499) 


64  Signal  Corps  Manual  No.  3. — Chapter  1 1 . 

It  is  found  better  to  go  alternately  too  low  and  too  high  rather  than  twice  on 
the  same  side.  Also  it  is  recommended  that  when  nearly  the  same  at  both  ends 
measurements  should  be  repeated  to  check  errors. 

Supposing  the  resistance  of  the  cable  when  sound  (L)  to  be  4,500  ohms,  then  by 

L  —  r 
the  formula  — tt^—^ 

^555^1^=1,915  ohms  from  B  to  the  fault. 

For  further  information  concerning  this  test  refer  to  Jordan's  and  Schonau's 
inoditication  of  Keuneley's  and  Anderson's  earth-overlap  test  in  "  Handy  For- 
mulae for  Testing  Submarine  Cable  for  Breaks,  Dead  Grounds  and  Earth  Over- 
lap," appearing  later  in  this  chapter.  Also  see  "  Beginners'  Manual  of  Sub- 
marine (Jal)le,"  by  Baines,  page  132. 

The  advantage  of  testing  by  varying  the  current  is  that  there  need  be  no 
cooperation  between  distant  stations ;  the  testing  is  done  by  one  man,  while 
Clark's  potential  test  and  the  earth-overlap  tests  require  cooperation  between 
stations,  with  possibility  of  delay  and  disagreement,  unless  well  arranged  for 
before  undertaken. 

However,  the  Clark's  potential  and  the  earth-overlap  tests  are  particularly 
applicable  to  locating  high-resistance  faults,  through  which  it  would  be  im- 
possible or  impracticable  to  force  enough  current  to  vary  sutticiently  to  form  a 
Jona  curve,  or  ai»ply  to  formuhe  using  .similar  data. 

Should  the  cable  have  more  than  one  fault,  the  result  foinid  will  lie  somewhere 
between  the  t\V(»  actual  faults  and  nearer  Id  the  fault  wilh  Ihe  least  resistance. 
This  remark  applies  to  all  tests. 

HAXDY     t'OKMULAE     FOR     TIOSTING     Sl'BMARINE     CABLE     1  Oli     BREAKS,     DEAD     GROUNDS, 

AND    EARTH     OVERLAP. 

Location  of  cable  faults  can  not  be  definitely  made  where  there  is  not  a 
metallic  circuit.  Where  part  of  the  testing  cm-rent  passes  through  water,  de- 
composition takes  place  at  the  fault  and  the  resistance  of  the  fault  is  con- 
stantly chiinging. 

It  has  been  found  by  practice  that  the  resistance  of  such  a  fault  varies 
inversely  as  the  square  root  of  the  testing  current,  provided  the  exposed 
surface  of  tlie  contluctor  be  not  less  than  one-half  of  a  square  centimeter, 
and  the  testing  current  does  not  exceed  24  milliamperes. 

SCALE ZERO. 

[Not  metallic  circuit.] 

No.  1,  Jona  curve  (see  curve  sheet  fig.  11-42).  Preferable  to  use  exact  num- 
ber milliamperes,  as  printed  on  left-hand  edge  of  sheet. 

Tln'  .Jona  curve  is  based  on  variations  of  current;  the  regularity  of  the 
curve  shows  tlie  dependence  to  be  placed  on  the  tests.  The  scale  zero  is 
u.sed.  The  data  may  also  be  used  for  solving  other  scale  zero  fornmlse.  The 
regularity  of  the  curve  is  very  imi)ortant.  I'sually  the  other  formuliie  using 
this  data  means  nnich  increased  work,  witii  little  additional  advantage.  (See 
the  actual  test  shown  below.) 

From  the  measurements  for  the  above  Jona  curve,  scale  zero,  2  to  24 
milliamperes,  the  following  formulae  can  be  worked  out  and  used  for  check- 
ing puri)oses,  (tr  in  deriving  a  mean  result. 

For  nrdformity,  tlie  designations  below  of  (7— current  and  i2= resistance, 
and  tlieir  relations  to  each  othei-  should  he  maintained. 

(500) 


Long  Submarine  Cables,  Telegraphy,  and  Tests. — Chapter  1 1 . 


65 


I 


('i  =  lo\vest  current=hiKlu'st  resistance=/23 

C2= intermediate  ourreut=iiiteriMeiliate  resistance— II2 

C3=liif?liest  i-urrent=lo\vest  resistance=72i 

No.  2.  (Mann's  trii)U>-tost  (p.  00,  Barkers  Hanrlbook,  1903)  : 

r,    C,    Cz 

Current  ratio  :     1:2:4     — Scale  zero. 

Hi     Hi     R\ 

X=Ri-\-R—IU 

Note. — Can   iret  six   ciiiculMlifins   Irom   .Toiia   measurements  for   \\w  i)racti('al 

(ests  ai)pen(le(I   iiereto. 

Usin.u-  Ma         Ma.         Ma 

2,  4  juul     S 

3,  6  and  12 

4,  8  and  16 

5,  10  and  20 

6,  12  and  24 

8,  IG  and  82     approximating:  for  32. 

No.  3.  Rynier-.Toncs  dual  test,  modification  of  Cann's   (p.  01,  liarker's  Hand- 
l)ook,  1003). 

Turrent  ratio:  1  :  2  —scale  zero. 
R,    R, 
A'=2.5576  i?i-1.5576  R^ 
Note. — Can  ,iret  eiijlit  calculations,  hut  tlie  two  lowest  are  too  small  ;  po.ssibly 
only  one  lowest  too  snuill.     See  practical  test  annexed. 


Jsin,^  Ma.         Ma 

Using  Ma.        Ma. 

2  and     4 

6  and  12 

3  and     G 

8  and  16 

4  and     8 

10  and  20 

5  and  10 

12  and  24 

For 

tise  in  Rymer-.I 

mes  dual  cable  test. 

1X15,576  equals 

15.576 

1X25.576  equals 

25.576 

2X15.576  equals 

31,152 

2X25.576  equals 

51.152 

3X15.576  equals 

46,728 

3X25,576  equals 

76.728 

4X15.576  equals 

62.304 

4X25,576  equals 

102,304 

5X15,576  equals 

77,880 

5X25,576  equals 

127,880 

6X15,576  equals 

93.4r.(i 

6X25,576  equals 

153,456 

7X15,576  equals 

109,032 

7X25,576  equals 

179.032 

8X15,576  equals 

124,608 

8X25,576  equals 

204,CR)8 

9X15.576  equals 

140,184 

9X25.576  equals 

230,184 

No.  4.  Kennelly   (p.  (il,  I'.arker's  Handbook,  1903). 

(\    c,   c. 

Current  radio:  1:     4:9    —scale  zero. 

Rs    ^2    lii 

A'=:?i±^'-4(/?3-i?,) 

Note. — Two  calculalion.s,  approximate  for  27  and  18  milliamperes. 

(^3  ma.   :   12  ma.  :   27  ma.-i 

[2  ma,    :     8  ma.'  :   IS  ma.j 
See  practical  tests  appended  hereto. 

(501) 


66 


Signal  Corps  Manual  No.  3. — Chapter  II. 


No. 


5.  Keunelly.     Ps 

ge  62, 

Barker's  Handbook,  1903. 

Cy 

C, 

Cs 

Current  ratio:  1 

:  4    : 

16    —scale  zero. 

Rz 

i?2 

^1 

Note. — This  test  not  limited  to  25  milliamperes,  according  to  Kennelly. 
Note. — Two  calculations,  approximate  for  32  and  48  milliamperes. 

2  ma.   :      3  ma.   :  32  ma.)     o  t^-     i  4-    <  i 

^         >    See  practical  tests  annexed. 

3  ma.   :     12  ma.    :  43  ma. J 

Note  for  approximating.— It  is  noticed  that  the  difference  between  readings 
grows  less  as  ma.  increases;  also  that  12,  16,  20,  24  differ  by  4;  hence,  32 
greater  by  two  periods  of  4  than  24  which  is  measured. 

Also,  that  48  is  greater  by  6  periods  of  4  than  24  which  is  measured. 

Diminish  the  difference  between  fours  as  they  increase,  being  guitled  by  the 
differences  measured  between  12  and  24. 

Heavy  solid  black  curve  shows  estimated  96  ohms;  heavy  dotted  black  curve 
shows  that  it  should  have  been  103  ohms.  Fine  solid  curve  shows  estimated 
curve,  196  ohms ;  tine  dotted  curve  shows  that  it  should  have  been  203  ohms. 


708090100    120    140    160    180   200  220  240  260  280  300  320  340  360  380  400 

OOQOOOOOOOQOOOOQ 


OHMS    O 


S       Ig 


Fig.   11-42.— LONG    SUBMARINE     CABLES,    TESTING,    CURVE    SHEET    FOR    JONA    AND 

OTHER    GRAPHS. 

(602) 


Long  Submarine  Cables,  Telegraphy,  and  Tests. — Chapter  11.  67 

Two  Actual  Laboratory  Tests,  One  With  103  Ohms  in  CiBcmT,  the  Other 
With  202  Ohms  in  Circuit,  Ends  Terminating  in  Glass  Jar  Filled  With 
Sea  Water,  Exposure  ok  Ends  Being  :  102  Ohms,  J  Inch  ;  and  203  Ohms, 
Copper  Flush  With  Insulation. 

[100  ohms  in  rheostat — 2  milameters  3  ohms^l03  ohms  in  circuit.] 

Measnrements. 

[One-half  inch  core  exposure.    Scale  zero.] 

actual  test. 


Milliamperes. 

Ohms. 

24 

144 

20 

1.50 

10 

158 

12 

171 

10 

164 

8 

193 

6 

21.5 

5 

233 

4 

2.55 

3 

299 

o 

384 

C 

atriit 

\  fit  ions. 

CANN  S  TRIPLE  TEST. 
Scale  zero. 
109 
110 
112 
109 
105 
80 

6)631 


Average-  105.2  ohms. 


RYMER-.IONES  DUAL  TEST. 
Scale  zero. 

102 

97.1 
103.5 
102.5 
107.5 

96.4 

(84)  excluikHl 
(54)  excluded 


kennelly's. 

Scale  zero. 

1:4:9  milliamperes,  ratio  of. 
Can  get  2  calculations. 
3  ma. :  12  ma. :  27  ma.=100     ohms. 
2  ma. :    8  ma. :  18  ma.  =  108.5  ohms. 


2)208.5  ohms. 
Average 104.2  ohms. 


0)409.0 
Average-  101.5  oliins. 


Highest. 
Lowest-. 


112 


ohms.  Highest  -  107.5  ohms, 
ohms.  1^0 west 96.4  ohms. 


2)  203.9  ohms. 


2)198     ohms. 
Average-    99     ohms.  Average-  101.9  ohms. 

Note. — See  curve  slieel  lor  ,Jona  curve. 


kennelly's. 
Scale  zero. 

1 :  4 :  16  milliamperes,  ratio  of. 
Get  two  calculations. 
2ma. :    8  ma. :  32  ma.  =  110    ohms. 
3  ma. :  12  ma. :  48  ma. =106    ohms. 


Average 


2)210 
.     108 


ohms. 


(503) 


68  Signal  Corps  Manual  No.  3. — Chapter  II. 

General  average  of  all  the  lOS-ohin  test,  scale  zero. 

105.2 

99.0 
101.5 
101.9 
104.2 
108.0 

96.0  Joua  curve. 

7)715.8 
General  average-  102.2  ohms. 

Second   test :   200  ohms  in   rheostat— 2   milliamperes   3   uhms=203   ohms   in 
circuit. 


Mcusurcimnt 

s. 

[Core  flush. 

Scale 

zero.] 

ACTUAL 

TEST. 

Milliamperes. 

Ohms. 

24 

270.6 

20 

278.6 

16 

292.6 

12 

316.8 

10 

330.0 

8 

350.0 

6 

388.3 

5 

420.5 

4 

455.6 

3 

512.4 

2 

640.0 

Calculations. 
[liOo  ohms  circuit.] 


CANN  S  TRIPLE  TEST. 

UYMEK-.IONES  DUAL  TEST. 

Scali'  zero. 

■5cali"  zero. 

215 

199 

203 

199.5 

211 

206.7 

216 

206.4 

204 

190 

209 

185 

6)1,2.58 
Average-  209.7  ohms. 

195 
(169.4)  excluded 

IIiRhest-216 

7)1.381.6 

Lowest—  203 

Average 

.  197.4  ohms. 

2)419 

Highest 

.206.7 

Avernpo-  209.5  f>hnis. 

Lowest - 

2 

_185 

)391.7 

Average 

.  195.8  ohms. 

Note. — See  curve 

■^liccl   for 

.Tona  curve,  196 
(504) 

KENNELEYS. 

Scale  '/.(  ro. 

1:4:9:  millianiperos.  ratio  of. 
Can  get  2  calculations  only. 
3  ma. :  12  ma. :  27  ma. =181.5  ohms. 
2  ma. :    8  ma. :  18  ma. =202.5  ohms. 


2)384 
Average 192     ohms. 

KENNELEYS. 
Scale  zero. 
1 :  4 :  16 :  milliamperes.  ratio  of. 
Can  get  2  calculations  only. 
2ma. :    8  ma. :  32  ma. =207     ohms. 
3  ma. :  12  ma. :  48  ma. =213.2  ohms. 

2)420.2 

Average 210.1  ohms. 

ohms. 


Long  Submarine  Cables,  Telegraphy,  and  Tests. — Chapter   11.  69 

General  average  of  all  the  .iOJ-ohin  test. 

209.  7 

209.5 

197.4 

.     195.8 

196.0  Jona  curve. 

192.0 

210.1 


7)1,410..- 


201.5  ;j;t'iK'rul  average. 
203.0  uhnis  exact. 
Krror,  2.5  olinis. 

Refer  to  the  .Tona  curve  sheet,  where  IG  mil  amperes  are  used:  Then  V16=4; 
iiiv<M-s(>I.v  1=0.25,  whicli  will  he  found  opposite  10  on  right-hand  side  (tf  curve 
sheet,  indicating  that  tlie  resistance  of  tlie  fault  lias  heen  reduced  to  xVo  <^i  itself. 

Again,  where  4  mil  amperes  are  used:  v'4=2;  inversely  2=0.50,  which  will 
be  found  on  right-hand  side  of  the  curve  sheet  opposite  4,  which  shows  the 
resistance  of  tlie  fault  has  been  reduced  to  Ts^oi.  itself. 

It  will  again  he  observed  by  noting  the  curve  that  as  the  tests  approach  24 
mil  amperes  tlic  resistance  which  is  .sought  is  reduced. 

Solicitude  for  the  safety  of  the  instruments  and  cable,  together  with  exjie- 
rience.  has  shown  that  24  mil  amperes  should  not  be  exceeded. 

Casual  observation  of  the  fine  current  lines  on  the  .lona  curve  sheet,  together 
with  knowledge  of  tlie  direction  of  the  curve,  shows  that  after  24  mil  amperes 
are  jiassed  the  line  solid  and  dotted  lines  are  close  together,  even  though  the 
differences  are  8,  as  comiiared  with  differences  of  4  between  24  and  12,  and  2 
between  12  and  6,  and  1  between  6  and  2,  while  the  curve  itself  is  more  perpen- 
dicular, with  a  consequent  decrease  in  the  rate  at  which  the  resistance  is  being 
reduced. 

The  above  shows  that  after  passing  24  very  great  increase  in  current  is  neces- 
sary to  produce  a  small  decrease  in  resistance.  Hence,  the  curve  below  24  on 
the  sheet  is  approximated  as  being  the  most  practicable. 

Referring  to  the  numbers  on  the  right-hand  side  of  the  curve  sheet,  which 
are  the  results  of  1  divided  by  the  square  root  of  milliamperes  used,  it  will  be 
found  that  they  Increase  from  the  bottom  to  the  top  of  the  page,  and  that  the 
distance  apart  is  regular,  while  the  distance  apart  of  the  tine  current  lines  is 
irregular. 

To  eliminate  all  resistance  in  the  fjuilt  would  require  an  infinitely  large  cur- 
rent, as  the  resistance  of  the  fault  is  proportional  to  the  numliers  on  right-hand 
side  of  the  curve  sheet,  i.  e.,  no  resistance  on  the  bottom  line,  increasing  to  0.70 
of  the  full  resistance  of  the  fault  at  2  milliamperes. 


(505» 


70  Signal  Corps  Manual  No.  3.— Chapter  11. 

Taking  the  two  examples  noted  above  and  deducing  from  percentage  of  fault 
to  mil  amperes  necessary — 

Let  A'=milliamperes  necessary. 

Then:     .50=i     •••     -50    V^=l  -••    V^=4t=2 
■yjx  -50 

-^ X  =2,  squaring  both  members^  x=4  agreeing  with  numbers  as  printed  on  curve 
sheet. 

Again:      .25=-7=     .".      .2b^jx=\     :.      V  ^  ~~9K~'^ 

■y/x=4,  then  by  squaring  both  members  .r=16. 

Using  the  experience  thus  gained  we  know  that  .00=-^  or  the  milliamperes  would 

have  to  be  infinitely  great  to  produce  no  resistance  in  the  fault. 

By  way  of  comparison,  however,  we  can  find  out  the  milliamperes  necessary  to 
reduce  the  resistance  of  fault  to  a  very  low  finite  quantity. 

Question :  Ho\\'  much  current  is  necessary  to  reduce  resistance  of  fault  to  .001 
of  itself  V 

.001=  ,        .-.     .  001-^^=1     .-.     ^/^= =1000 

■s/x  "  ^        .001 

Va-=1000,  .1  =  1,000,000  milliamperes,  which  is,  of  course,  impracticable. 

Tlie  above  calculations  in  practice  would  be  considerably  upset,  for  a  strong 
negative  current,  which  is  the  current  mostly  used,  would  insulate  or  tend  to 
insulate  the  exposed  surface  by  covering  it  with  liydrogen  gas,  for  the  stronger 
tbe  current  the  more  hydrogen  is  released.  If  positive  current  is  used  tlie 
copper  is  decomposed  and  the  exposed  end  is  covered  with  a  cuprous  or  copper 
powder  which,  as  well  as  the  hydrogen,  has  an  insulating  effect;  hydrogen  gas, 
however,  being  more  volatile  escapes  more  easily  except  when  formed  in  a  very 
small  aperture  sealing  it,  in  which  ca.se  it  is  sometimes  necessary  to  use  the 
positive  current  to  clear  off  the  hydrogen. 

Very  small  exposures  sometimes  are  highly  insulated  by  globules  of  hydrogen 
gas,  using  the  negative  current.  In  such  a  case,  a  very  strong  current  would 
burn  out  the  fault,  after  which  a  weaker  current  could  be  used  for  testing. 

Current  used  should  not  exceed  24  milliamperes  and  in  case  of  higli  resistance 
faults  this  could  be  obtained  M'ith  the  limit  of  40  volts.  These  limitations  are 
necessary  for  the  safety  of  the  cable. 

HANDY    FORMULA    FOR    TESTING    SUBMARINE    CAHLK    FOR    1U5FAKS    OR    np;AI)    GROUNDS. 

[Not  metallic  circuit.] 

No.  C.  I'age  i;?2  Raines  Begiinier's  Manual,  second  edition;  page  145 
Fislier  &  Darby,  tliird  edition,  for  Jordan  and  Sclionau's  modification,  of 
Kenneley's  and  Anderson's  earth  overlap  test. 

The  plain  earth  overlap  test  lias  been  i)reviously  (>xi)lMin(Ml  in  (bis  chapter. 

Tests  are  taken  by  each  station  under  similar  conditions  or  bridge  ratio, 
battery  power,  etc.,  until  preconcerted  number  of  observatioius  have  been 
completed. 


(506) 


Long  Submarine  Cables,  Telegraphy,  and  Tests. — Chapter  II.  71 

atationH  Nioiihrrcd  1  and  2. 

[First  operation — I'roliminary  tost.] 

Station  2  cable  ffroundod. 
Station  1  nieasun'  rosistancc  (R). 
Station  1  ciihle  firounded. 
Station  2  measure  resistance   (li'). 

I  Second  operation.] 

Stalioii  1   niipliii,'  in  liridtje  R  +  R\ 

Station  2  uiii)hm  in  l)ridKe  R  +  R^. 

Station  1  in.sert  resistance=A''  Ijetwccn  liri(l;:('  jiiid  calilc  — call   i1    (?•). 

Station  2  insert  resistance^A'  l)et\V(-en  i)ri(i;:("  and  cable— call  it   (r'). 

I'I'liird  operation — I-'or  test,  j 

Stalion  2  ground  cal)le,  leaving;  /•'  in  circuit. 

Station  1  obtain  balance  in  bridge  by  increasing  or  decreasinu  tlic  value  of  r. 

Station  1  ground  cable,  leaving  r  in  circuit. 

Station  2  obtain  balance  in  bridge  by  increasing  or  decreasing  the  value  of  i-'. 

This  operation  to  be  repeated  alternately  by  stations  ]   and  2  until  balance 
is  obtained  without  having  to  make  furl  her  changes  in  resistance  r  or  /•'. 
Then  the  resistance  to  the  fault  from  station  1  is — 


L+r^-r 


and  from  station  2: 


L+r-r' 


=ohms  to  fault. 


=ohms  to  fault. 


2 

/>=length  of  perfect  cable  in  ohms. 

The  sum  of  these  two  results  should  equal  the  C.  R.  of  the  perfect  cable. 

For  the  purpo.se  of  checking  the  battery,  which  should  be  the  same  at  both 
ends  of  the  cable,  a  milliamineter  should  be  inserted  in  the  cable  and  the  read- 
ings taken,  and  when  the  fault  has  been  electrically  placed  in  the  center  of 
the  cable  the  readings  of  the  milliammeters  at  both  ends  of  the  cable  should 
be  the  same. 

JORDAN   AND   SCHONAU'S    MODIFICATION. 

For  a  continuation  of  the  foregiting  tests,  another  series  was  taken  to  a 
diminished  resistance  in  C.  The  inserted  resistance  r  at  station  1  being  the 
lowest,  viz,  4.124  ohms,  each  end  could  be  reduced  4,000  ohms  in  C  (arm  of 
bridge,  .see  diagram).  The  amount  therefore  in  (',  at  both  stations,  to  which 
balance  would  be  obtained  by  the  respective  adjustments  of  r  and  /•*  was 
made  5,810  ohms. 

It  will  be  seen  from  the  following  res\dts  that  r  and  /•'  were  proportionately 
diminished! 

Station  1.  Station  2. 

1st  test,  r  IfiG  r',  1..3.34 

2d  test,  r  162  r',  1,334 

3d  test,  r  162  rK  1,3.34 

4th  test,  r  162  r',  1,334 

46581°— 17 33  (507) 


72  Signal  Corps  Manual  No.  3. — Chapter  11, 

The  resistance  to  the  fault  from  station  1  is: 


and  from  station  2: 


8800+1334- 162_^  986 
2 


8,800+162- 1,334_3  g^^ 


which  results  are  the  same  as  those  obtained  wdth  9,810  ohms  in  C,  for  the  first  series 
of  tests. 

4,986+3,814=  ohms  total  8,800 

EIXAMPLE  OF  JORDAN  ANDSCHONAU5  MODIFICATION 


Ahnjltdevdapedinacahkcf  88CO  ohms  when perfecl-.  Per  ttshcalnabon  20  LccJandK  cfJi^  ■ 

FIRST  OPERATION 

Preliminary  Test 


i  at  ojcS  staOon  and  a  badge  rata  of  tCOO/lOOO 


H>i  f^n 


STATION  2      T  T 

I       Ground         \_  J^, 


SECOND  OPERATION 

neifihurb'imcoppemsjsianc^s.a^urifa ttbt  i&iO ohm\^¥i^s unplugged m hofh bndaf  i) 


jgr-FTCi 


Fig.  11-43.— LONG    SUBMARINE    CABLES,    TESTING,   JORDAN    AND    SCHONAU'S    MODI- 
FICATION   OF    EARTH     OVERLAP    TEST,    DIAGRAM     OF    CONNECTIONS. 

INSTRUCTIONS    FOR    SHORE    STATIONS    DX'RING   LAYING    OR    KEP.MR    OF    CABLE. 

Instructions  will  be  given  to  look  out  for  .ship's  call  at  a  specified  time. 
CJonnect  up  for  receiving,  and  keep  close  watch  in  order  to  answer  promptly. 

Ship  will  give  instructions  regarding  nece.ssary  connections.  These  instruc- 
tions must  he  implicitly  obeyed,  and  with  rigid  accuracy  as  to  time. 

Timer)ieces  are  to  be  set  according  to  ship's  instructions,  and  frequent  com- 
parisons with  ship's  time  made  in  case  timepiece  is  not  regular. 

Instructions  to  "  free  the  end  of  the  cable  for  so  many  minutes  "  would  be 

abbreviated  "  Free min."     During  this  period  especial  care  must  be  taken 

that  the  end  is  well  insulated,  and  on  no  account  must  the  c(mductor  Vie  per- 
mitted to  touch  anything. 

Instructions   t<i   "  Karth    (ground)    the  ciililc   for  so   many   niiiuitcs  "   will   be 

al)brcviated  "  Karth  min."     The  end  of  the  conductor,  or  its  binding  screw, 

will  then  Im'  directly  and  secuicly  connected  to  the  cable  armor  for  the  time 
specified. 


(508) 


Long  Submarine  Cables,  Telegraphy,  and  Tests. — Chapter  II.  73 

After  each  orcter  is  executed  for  the  time  .specified,  connect  up  for  receiving 
jind  await  next  order.  Should  no  communication  come  from  the  ship  after 
15  minutes,  begi^i  at  the  hour  and  free  the  cable  for  15  minutes,  then  earth 
f<»r  15  minutes,  then  connect  up  U>v  receiving  during  the  remaining  half  hour. 
(Continue  this  routine  every  hmii-  until  connnunlcation  is  restored,  or  twelve 
hours  has  elapsed.  If  there  is  still  no  communication,  connect  up  for  receiving 
and  keep  close  watch  for  ship's  call. 

In  a  book  at  the  station  will  be  kept  a  complete  record  of  all  changes  in 
connections  made  and  instructions  received  during  laying  and  repairs  and 
the  exact  time  each  was  made.  This  record  must  be  signeil  by  the  man  on  duty, 
with  note  of  time  he  has  been  relieved.  He  will  at  the  same  time  call  atten- 
tion of  the  one  relieving  him  to  any  written  note  of  instructions  he  has  received 
from  the  ship. 

Strict  obedience  to  the  foregoing  instructions  is  enjoined. 

Ahifskan   cnblc  data. 
[Weight  of  1903  tjTe.] 


AMiole  cable  in  air  (per  knot ) .• 

Whole  cable  in  air  (per  mile ) 

Whole  cable  in  water  (per  knot) 

Whole  cable  in  water  (per  mile) 

MATERI.\LS. 

Iron  wire  (per  knot ) 

Iron  wire  (per  mile) 

Jute  and  compound  (per  knot) 

Jute  and  compound  (per  mile) 

Tape  (per  knol ) 

Tape  (per  mile) 

Rul)ber  (per  knot) 

Rubber  (per  mile) 

Copper  (per  knot ) 

Copper  (per  mile) 

Diameters inch . . 

C.  R.  at60°  F.  (per  mile) ohms.. 

D.  R.  at  60°  F.  (per  mile) megs.. 

Capacity  (per  mne) m.  f . . 

C.  R .  at  60°  F.  (per  knot ) ohms. . 

D.  R.  at  60°  F.  (per  knot) megs. . 

Capacity  (per  knot) m.  f . . 

Breaking  strain 

Elastic  strain 


Deep 
sea. 

Interme- 
diate. 

S.  E. 

Pounds. 
3,605 
3,127 
2,328 
2,019 

2,359 

2,046 

888 

770 

66 

Pounds. 

6,787 
5,887 
4,812 
4,174 

5,083 
4,409 
1,341 
1,163 

Pounds 
21,620 

18,800 

57 

177 

153 

132 

115 

.81 
7.39 

.98 

1.75 

1,418 

.428 

8.52 

1,230 

.493 

14, 570 
11,000 

19,790 
13,000 

Note. — Alaskan  tj-pe  of  1904  has  215  pounds  of  rubber  per  knot. 

Shore  end  is  intermediate  (11  No.  8  B.  \V.  G.  wires)  withanoulerarmorof  13No.  SB.  W.  G.  wires. 


(509) 


74  Signal  Corps  Manual  No.  3. — Chapter  11. 

Weights  (in  pounds)  siibnidrinc  cable,  Alaskan  ti/pr,  1905. 


Per  mile. 


Per  naut. 
mile. 


Core: 

Conductor 

Pure  Para 

40  per  cent  compound. 
Tape 


Total. 


Deep-sea  cable: 

Core 

Armor  (16  No.  i;3  B.  W.  G.  wires). 
Jute,  tar  compound,  and  cutch 


Total 

Weight  in  water. 


Intermediate  cable: 

Core 

Armor  (11  No.  8  B.  W.  G.  wires). 
Jute,  tar  compound,  and  cutch. . . 


Total 

Weight  in  water . 


Shore-end  cable: 

Core 

Armor(flrst,  11  No.  8B.  W.  G.)... 
Armor  (second,  14  No.  .3  B.  W.  G.). 
Jute,  tar  compound,  and  cutch 


Total 

AVeightin  water. 


Specific  gravity: 

Pure  Para 

40  per  cent  compound. 


Pounds. 
122.  48 

11.38 
193. 31 

71.00 


39S.  17 


398. 17 

2, 232. 00 

656. 00 


3,286.17 
2,098.00 


398. 17 
4,690.00 
1,  l:JS.  00 


6,226.17 
3,948.00 


.398.17 
4,690.00 
13, 002.  (X) 
3,430.00 


21,520.17 
15, 192. 00 


Pounds. 

141.18 

13.10 

222.60 

81.75 


458. 63 


458. 63 

2,570.00 

755. 40 


3,784.03 
2,416.00 


458.63 
5, 400. 20 
1,310.30 


7, 169. 13 
4,546.00 


458. 63 
5, 400. 20 
14,972.00 
3,949.00 


24, 779. 83 
17,495.00 


.9250 
1.5903 


(510) 


INDEX. 


REMARKS. 

All  those  to  whom  this  manual  is  issued  are  recjuested  to  observe  that  the  index  consists  of  three  parts, 
namely:  Chapters,  subjects,  and  ilUislrulions;  and  that  to  find  a  subject  or  illustration  it  is  first  necessary 
to  locate  the  chapter.  This  can  be  readily  accomplished,  as  chapter  numbers  appear  on  each  leaf  of  the 
manual. 

An  alphaljetically  arranged  list  of  all  Signal  Corps  apparatus  and  supplies  appears  in  chapter  8,  begin- 
ning on  page  1. 


CHAPTER    INDEX. 


CHAPTER  1. 

The  Voltaic  Cell,  Ohms  Law,  and  Primary  anu  Secondary  Batteries. 

CHAPTER  2. 

Telegraphy'  and  the  Induction  Telegraph  Set. 

CHAPTER  3. 

Telephony,  the  Camp  Telephone,  and  the  Buzzbr. 

.  CHAPTER  4. 

Cable  and  Cable  Systems. 

CHAPTER  5. 

Aerial  Line  Construction. 

CHAPTER  6. 

Post  Telephone  Systems. 

chapter  7. 

Small  Arms  Target  Range  Signaling  Systems. 

chapter  8. 

Technical  Equipment  Issued  by  the  Signal  Corps. 

CHAPTER  9. 

Miscellaneous  Tests  and  General  Information. 

CHAPTER  10. 

Requisitions  and  General  Maintenance  Regulations. 

chapter  11. 

Long  Submarine  Cables;  Submarine  Telegraphy;  Tests  op  Submarine  Cables. 

(511)  1 


I 


SUBJECT    INDEX. 


Subjects. 


A. 

Accuraulation  of  sediment  in  storage  batteries 

Action  of  buzzer  interrupter , 

Adjustment  of  telegraph  apparatus , 

Aerial  cal>le,  installation  of , 

Aerial  line  construction: 

Amounts  of  sag  of  aerial  wires , 

At  crossings 

Attaching  guys  to  rook 

Attaching  guys  to  trees 

Bracket  lines 

Cable  box 

Cable  box  ground,  lapping  for  splices  and  sealing  cable  ends 

Cable  terminals,  fused  and  unf used 

Connect  aerial  line  through  fuses  and  Lightning  arresters 

Connecting  aerial  wires  to  cable 

Crossing  a  road 

Dimensions  of  cross-arms 

Double  arms 

Drip  loops 

Employed  at  Front  Royal,  Va.,  Remount  Depot 

Erection  of  line,  method  of  procediu^e 

Fence  post  lines 

Galvanized-iron  wire,  for  guying  light  lines 

Guard  wires 

Guy  rods,  deadman,  thimbles 

Guys  and  anchors 

Guy  stubs  and  anchor  logs 

Guy  terminal  cross-arm 

Handling  and  hanging  cable  to  messenger 

Handling  hard-drawn  copper  wire 

In  rolling  country 

Insulators 

Lightning  rods 

Linemen  not  to  use  climbers  on  stepped  poles 

Long  spans 

Construction  of  saddles 

River  crossing  at  Ruby,  Alaska 

Terminating  supports 

Wire  used 

Yukon  River  crossings 

Messenger  strand — ■ 

Amount  of  sag 

Ending 

Grading 

Guying 

Installing 

Metal  shims  for 

Properties  of  various  sizes 

Supports 

Terminating 

To  splice 

Turning  a  corner  with 


Chap- 
ter 
No. 


Chap- 
ter 

page 
No. 


See  Chap.  8,  p.  1,  for  alphabetical  list  of  all  Signal  Corps  apparatus  and  supplies. 

(518)  8 


Subject  Index. 


Subjects. 


Chap- 
ter 
No. 


Chap- 
ter 

page 
No. 


Aerial  line  construction— Continued. 

Poles,  concrete,  construction  and  dimensions 

Poles,  steel,  use  of 

Poles,  wood — 

Delivery  of 

Depth  to  set  in  ground 

Desired  dimensions 

Digging  holes 

In  Alaska 

Effect  of  treating 

Framing 

Location  of  gains 

Grading 

Line  for  aerial  cable 

Preparation  of 

Principal  factor  in  treating 

Setting 

Sides  to  use  for  cross-arms 

Species,  etc 

The  pole  brace  and  guy  stub 

Turning  a  right  angle  corner  with  two  poles 

Use  of  short  stout  poles 

Porcelain-coated  bridle  rings  for  supporting  bridle  wire 

Protection  of  aerial  cable 

River  crossings 

Self-supporting  tripods 

Size  of  guys  to  use 

Splicing  bridle  wire  to  copper  line  wire 

Stringing  wire 

Terminal  or  office  pole ■. 

Termination  of  line  at  buildings  other  than  residences 

Termination  of  line  at  residences 

Test  station 

Transposition  of  metallic  circuit 

Tripod  lines .- 

Poles  for,  and  erecting  the  tripods 

Two  methods  of  stringing  wire • 

Tying  in  copper,  iron,  and  steel  wire 

Wire  used  for  post  telephone  systems 

Aeroplane  tool  chests  and  contents 

Alaskan  cable  data 

Alaskan  lines: 

Diggi  iig  pole  holes 

lioag  spans 

At  Rul)y,  Alaska 

Construction  of  saddles 

Terminating  supports 

Wire  used 

Yukon  River  crossing 

ReIf-Hui)|)ort!ng  tripods 

Tri|)od  lines 

Alternating  ( inrtMit 

Cycles 

Produced  in  telephony 

Alphabeti<ally  arranged  enumeration  of  technical  equipment  issued 

l)y  the  Signal  Clorps 

Ainpcrc,  d<'fin<'d 

Anchors,  screw 

Anemometer,  portable,  for  small-armfl  target  ranges 

Apjjaratus,  tel<;grapli,  adjustincmt  for  maximum  strength. 


See  Chap.  8,  p.  1,  for  alphabetical  list  of  all  Signal  Corps  apparatus  and  supplies. 


(014) 


Subject  Index. 


Sul)jt'cts. 


Armor  (sheathing)  wires,  to  determine  number  required. 

Artificial  line,  duplex  telegraphy 

Automatic  transmitter  for  use  on  long  submarine  cables. 


B. 


Bag,  tool  service,  and  contents 8  68 

Batteries: 

Comparative  merits  ascertained 

Closed  circuit 

Closed  circuit,  service  used  for 

Closed  circuit,  t>'pes  used  by  the  Signal  Corps 

Dry  cells,  internal  resistance  and  weights 

Dry  cells,  testing 

Dry,  maintenance  of 10 

Dry,  t>^es  used  with  various  apparatus 

To  reju\'enate 

Duplex  telegraphy 

Edison  primary,  type  ^ 

Fuller 

Fuller,  deterioration  with  age 

Gravity  cell 

Gravity  cell,  internal  resistance  and  voltage 

Number  and  kind  required  for  various  Signal  Corps  apparatus. 

Open  circuit 

Oi)en  circuit,  service  used  for 

Primary 

Reserve  type 

To  place  in  service 

To  rejuvenate 

Secondary,  general 

Secondary,  how  known 

Service  testing 

Storage — 

Accumulation  of  sediment 

Additional  instructions  for  erecting 

Care  of 

Coimecting  the  charging  circuit 

Construction  of  racks 

Edison 

Electric  Storage  Battery  Co.'s  table  of  ratings 

General 

General  data  concerning 

Height  of  electrolyte 

Impmities  in  electrolyte 

Initial  charge — 

Chloride  accumulator 

For  various  makes 

Gould 

Willard 

Instructions  relative  to  installing  and  initial  charge 

Location  of 

Makes  in  use  by  the  Signal  (^orps 

Number  of  cells  supplied  for  C.  B.  post  telephone  systems 

Overcharge 

Pilot  cell 

Power  requii-ed  for  initial  charge 

Placing  out  of  service 

Placing  in  service  after  being  out  of  service 

Preparing  electrolyte 

Purposes  for  wliich  supplied 

See  Chap.  8,  p.  1,  for  alphabetical  list  of  all  Signal  Corps  apparatus  and  supplies. 

(ol5) 


("liap- 
tcr 
.No. 


Chap- 
ter 

page 
No. 


34 
17 
26 


Subject  Index. 


Subjects. 


Chap- 
ter 

No. 


Batteries — Continued. 
Storage — Continued . 

Regular  charge. 

Report,  monthly 

Table  showing  sizes  and  ratings 

Temperature  effects 

Tests  of  electrolyte 

To  raise  specific  gravity  of  electrol>i;e 

Treatment  of,  when  battery  is  to  stand  idle 

\Miy  they  should  not  remain  in  a  discharged  condition. 

Supplied  by  the  Signal  Corps 

The  dry  battery 

To  determine  how  to  connect 

Tungsten,  type  A 

Voltage  and  internal  resistance  of  various  types 

Voltage  used  for  cormnon  battery  post  telephone  systems. . . 
Bells,  extension: 

How  to  connect » 

Loud  ringing  and  indoor  type 

Blank  forms  of  Signal  Corps,  where  enumeration  may  be  found . 

Bolts,  toggle 

Box: 

Cable,  use  of 

Distributing,  for  target  ranges 

Junction,  target  range 

Terminal — 

General 

Metal — 

First  model 

Terminal  strip  used 

1915  model 

Box,  100,000  ohm,  standard. 


Bridge  type  of  duplex  telegraphy 

Bridge,  Wheatstone: 

Graphical  demonstration 

Post-office  type 

Precautions  in  operating 

Principle  explained 

Simplest  measurement 

Used  at  Alaskan  cable  offices 

Bridle  rings 

Bridle  wire 

Buzzer  connectors 

Buzzer,  service 

Action  of  interrupter 

Circuits  classified  and  traced 

Construction  described 

Cord,  plug,  line  connector,  and  ground  rod 

Instruments  it  replaces 

Interrupter  and  transmitter  circuits  combined 

Its  use 

Mutual  and  self-induction  defined 

Operation  defined 

Signals  exchanged  with  line  open 

Simplified  "through  circuits"  when  sending  Morse  signals. 

Theory  of  ol)Holete  field  buzzer 

To  operate  on  existing  telegraph  lines 

Used  as  a  telephone  or  telegraph  instrument 

Weight  of,  comjjlete 

Buzzer  wire 


1 
10 
1 
1 
1 
1 
1 
1 
1 
1 
1 
1 
9 
G 


See  Chap.  8,  p.  1,  for  alphabetical  list  of  all  Signal  Corps  apparatus  and  supplies. 

(510) 


Subject  Index. 


Subjects. 


Chap- 
ter 

page 
No. 


Cable:  ^• 

And  cable  systems 

Books  supplied  on  cable  testing 

Capacity  measurements  when  cable  exceeds  100  miles  in  length ...        11 

Classified 4 

Determination  of  number  of  sheathing  (armor)  wires  required  ....         9 

Electrolysis  and  remedy 4 

Grapnels  ut?ed  in  recovering  submarine  cable '       H 

Gutta-percha  insulation 11 

Handhng  and  hanging  to  aerial  messenger 5 

Installation  of — 

Aerial  cable 4 

General 4 

Submarine 4 

Precautions  to  avoid  rupture 4 

Underground- 
Avoiding  pulling  a  second  cable  in  conduit 4 

Branching  conduit 4 

Characteristics  of  fiber  conduit 4 

Connection  to  aerial  cable 4 

Conduit  construction 4 

Construction  of  manholes 4 

Handholes 4 

Manholes 4 

Formula  for  mixing  concrete 4 

Method  of  mixing  concrete 4 

Procedure 4 

Pulling  cable  in  conduit 4 

Racking,  tagging,  and  recording 4 

Trenching 4 

Two  methods 4 

Ty^pes  of  conduit 4 

Lapping  for  splice  and  sealing  ends 5 

Paper  insulation — 
Armored — 

Detailed  characteristics  of  all  types •. 

Dimensions  and  weights  of  shipping  reel 8 

Weights  and  lengths 8 

Lead-covered,  unarmored — 

Detailed  characteristics  of  all  types 

Lengths  and  reels 

Power 

Detailed  characteristics  of  all  types 

Special  types  that  have  been  purchased 

Usually  in  Signal  Corps  stock 

Protection  of  aerial  installations 

Reels,  and  their  numbers 

Collect  a  quantity  before  return 

Return  lagging  to  reels 

Relative  to  all  cable  used  by  Signal  Corps 

Rubber  insulation —  ! 

Submarine —  I 

Detailed  characteristics  of  all  types 

Lengths 

Weights ■ 

Subterranean —  ; 

Detailed  characteristics  of  all  types ! 

Lengths | 

Weights 

Splicer's  tool  chest  and  contents 

See  Chap.  8,  p.  1,  for  alphabetical  list  of  all  Signal  Corps  apparatus  and  supplies. 

(517) 


8 
4 

29 

7 

5 

27 

4 

7 

4 

8 

4 

8 

8 

24 

8 

25 

8 

26 

8 

27 

8 

27 

8 

27 

8 

27 

8 

64 

Subject  Index. 


Subjects. 


Chap- 
ter 

page 
No. 


Cable — Continued. 
Splicing— 

General 

Gummed  ])aper  to  limit  wiped  joint 

Gutta-percha  insulation 

Lead  sleeves  for  various  sizes  of,  splices 

Paper  insulation  cables 

Material  required  for 

Boiling  out  a  splice 

Complete  splice  day  begun,  if  possible 

Connecting  the  conductors 

Detecting  presence  of  moisture 

Paper  insulation — 

Direction  for  setting  up  pothead 

Filling  pothead  with  compound 

Method  of  making  pothead 

Placing  paper  sleeves 

Pot  head,  determining  dimensions  of  lead  sleeves 

Preparation  for  lead  sleeves 

Seal  cable  ends 

Submarine 

Transpose  circuits 

Wrap  splice  with  muslin 

Rubber  insulation — 

Lead  covered  and  armored 

Materials  and  tools  required 

Plain  lead-covered  cable 

Materials  and  tools  required 

Pot  heads  for 

S.  C.  type  251  cable 

Using  manufactured  sleeve 

Submarine 

Materials  required 

Raw  joint  described 

Relative  to  acid  soldering  flux 

Various  vulcanizers 

Vulcanized  joint 

Solder  used 

Suggestions  concerning 

Three  way  or  "  Y  "  splices 

Placing  split  lead  sleeve 

Submarine^ 

Cal)le  gear  and  supplies 

General 

Gutta-percha  and  rubber  compound  insulation,  general. . . 
Long- 
Alaska  cable  data 

Arrangement  of  instruments  for  operating 

Arrangement  of  testing  set 

Automatic  transmitters 

Cable  testing 

Capacity   measurements    when    cable    exceeds 

miles  in  length 

Conductor  resistance 

])(!scrii)tion  of  Fisher  cal)le  testing  set,  No.  2 

Elimination  of  earth  current  effects 

Fisher  cable-lesting  set,  special  Wheatstone  bridge. 

M(ui.sining  capacity  with  Fisher  set 

Mea.suring  length  of  single  conductor  cable 

See  Chap.  8,  p.  1,  for  alphabetical  list  of  all  Signal  Corps  apparatus  and  supplies. 


100 


4 
4 
11 
4 
4 
4 
4 
4 
4 
4 

4 
4 
4 
4 
4 
4 
4 
4 
4 
4 

4 
4 
4 
4 
4 
4 
4 
4 
4 
4 
4 
4 
4 
4 
4 
4 
4 


(B18) 


Subject  Index. 


Subjects. 


laid 


Cable — Continued . 

Submarine — Continued. 
Long — Continued. 

Cable  testing — rontinued. 

Notes  on  capacity  measurements 

Recommended  treatises 

Sample  tost  sheet 

Special  instruments  used 

Wheatstone  bridge  used  at  Alaskan  offices  . . 
Cuttriss  automatic  transmitter 

Adjustment 

Data  pertaining  to  the  Sitka-Seattle  cable  when 

Excessive  voltage  not  to  be  used 

Faults  classified 

General 

Ground  connections  for  Morse  operation 

Grapnels  used  in  recovering 

Gutta-percha  insulation 

Instruments  for  Morse  operation 

Instructions  for  shore  stations  during  laying  or  repair  of 

cable 

Laying 

Laying  by  improvised  means 

Paying  out  the  cable , 

Lightning  arrester,  office  wiring , 

Location  of  faults , 

Clark's  potential  test , 

Classes  i  and  2 

Class  3 

Examples  of  Jordon  and  Schonaus  modification 

Formula  for  testing  for  breaks  or  grounds,  nonmetallic 
circuit 

Handy  formulae  for  testing  for  breaks  and  grounds. . . . 

Jordon  and  Schonaus  modification , 

Prof.  Keunelly's  method 

Two  laboratory  tests  explained 

Measin-ing  conductor  resistance  Ti-ith  Fisher  testing  set 

Measuring  insulation  with  Fisher  testing  set 

Method  of  obtaining  ground  near  large  cities 

Morse  telegi-aph,  double-current  operation 

Murray  loop  test  -n-ith  Fisher  testing  set , 

Notes  on  efficient  Morse  working 

Proper  touch  to  key 

Relays 

Repeaters 

Notes  on  efficient  working  of  a  station  and  on  common 

troubles 

Operation  of 

Single-current  open-circuit  repeater  set 

Using  Morse  telegi-aphic  apparatus 

Operation  of,  using  siphon  recorders 

Reflecting  galvanometer — 

A\Tton  universal  shunt 

D'Arsonval 

Remarks  on  the  shunt 

Shunts 

Sullivan 

Thomi)son 

See  Chap.  8,  p.  1,  for  alphabetical  list  of  all  Signal  Corps  apparatus  and 


11 
11 
11 
11 
11 
11 

n 
11 
11 
11 
11 
11 
11 
11 
11 

11 
11 
11 
11 
11 
11 
11 
11 
11 
11 

11 
11 
11 
11 
11 
11 
11 
11 
11 
11 
11 
11 
11 
11 

11 
11 
11 
11 
11 

11 
11 
11 
11 
n 
11 

supplies. 


(519.1 


10 


Subject  Index. 


Subjects. 


Chap- 
ter 
No. 


Chap- 
ter 

page 
No. 


Cable — Continued. 

Submarine — Continued . 
Long — Continued . 

Single-current  open-circuit  repeater  sets — 

Adjustment  of  sounders 

Transmitters 

With  polarized  relays 

Siphon  recorders 

Adjustment : 

Auxiliary  apparatus 

Care  of 

Hybrid  type 

Large  and  small 

Motor 

Operated  by  electric-light  current 

MuLrhead  vibrator 

Splicing  gutta-percha  insulation  cable 

Switchboards  used 

Termination  of  cable 

Transmitter  tape  perforator 

Use  of  dynamometer 

Varley  loop  test  with  Fisher  set 

Wrapping  of  brass  ribon 

Number  and  location  of  those  installed 

Paper  insulation 

Latest  approved  types 

Laying  in  emergency 

Reserve 

Rubber  insulation  latest  approved  types 

Rubber  insulation — 

Manner  of  applying  insulation 

Multiple  conductor 

Single  and  double  armor 

Telegraphy.     (See  Cable  submarine,  Long.) 

Subterranean 

Armored  when  trenched 

Double  lead  covered  for  marshes 

Subterranean,  paper  insulation,  latest  approved  types 

Paperinsulation,  double  lead  covered,  latest  approved  types. , 

Rubber  insulation,  latest  approved  types 

System  of  assigning  type  numbers 

Tank,  circular,  to  determine  capacity , 

Terminals,  fused  and  unfuscd , 

Testing.     (See  "Tests,ca  ble,"  for  ordinary  te.sts  of  cable.     Sec 
"  Cable,  submarine,  long,"  for  tests  of  long  submarine  cables.) 

Transfer  from  one  reel  to  another 

Where  connected  to  aerial  wire 

Camp  telephones.     (iSfc  Telephone,  camp.) 

Capacity  measurements 

Care  of  storage  batteries 

Cart,  signal 

E()uipraent 

Carrier,  wire 

(Jart,  Avire: 

Description,  and  how  used 

Type  L,  (^xtra  and  maintenance  parts 

Case,  electrical  instrument  and  contents 

Cedar  poles: 

Dimensions  and  weights 

Dimensions  and  weiirhlfl 


11 

11 

11 

11 

11 

11 

11 

31 

11 

U 

11 

11 

11 

11 

11 

11 

11 

11 

11 

9 

4 

4 

4 

4 

4 

4 
4 
4 

4 
4 
4 
4 
4 
4 
8 
9 
5 


See  Chap.  8,  p.  1,  for  alphabetical  list  of  all  Signal  Corps  apparatus  and  supplies. 


(520) 


Subject  Index. 


11 


Subjects. 


Cell: 

Battery,  determining  how  to  connect 

Dry  bat  tery 

Reserve  type 

Edison,  primary  battery,  type  V 

Fuller  battery 

Effect  of  age 

Gravity  battery. 

Internal  resistance  and  voltage 

Voltaic 

Polarity 

Cells,  battery,  number  and  kind  required  for  various  Signal  Corps 

apparatus 

Chatterton's  compound 

Chests : 

Pack,  how  used 

Tool- 
Aeroplane  and  contents 

Cable  splicer's  and  contents 

(Construction  and  contents 

Electrical  engineers  and  contents 

Mechanic's  and  contents 

Pipe  fitter's  and  contents 

Post  and  contents 

Clamp  and  pigtail  insulators 

Closed  circuit: 

Batteries 

Ser^•ice  used  for 

Type  supplied  by  Signal  Corps 

Telegraph  system 

Coefficient  temperature 

Of  various  metals 

Coil,  exploring: 

To  identify  cable  in  trench 

To  locate  a  ground 

Common  batterv  telephone : 
Desk— 

Garford  circuits 

North  Electric  Co.  circuits 

General 

Operation  explained 

Siunter,  wall,  circuits 

Systems,  number  of  cells  of  storage  batteries  used 

Transmission 

Wall- 
Circuits  traced 

North  Electric  Co.  circuits 

Western  Electric  Co.  circuits 

Compound : 

('hatterton's 

Gyite.. 

Insulutine 

Insulating 

Ozite,  three  grades 

Concrete: 

Formula  for  mixing 

Method  of  mixing 

Condenser: 

Defined 

Standard,  for  cable  testing 


Chap- 
ter 
No. 


Chap- 
ter 

page 
No. 


See  Chap.  8,  p.  1,  for  alphabetical  list  of  all  Signal  Corps  apparatus  and  supplies. 


(521) 


12 


Subject  Index.- 


Subjects. 


Chap- 
ter 

No. 


Chap- 
ter 
page 

No. 


ConductiAdty,  Matthiessen's  standard 

Conductor  resistance 

Conduit: 

Construction 

Characteristics  of  fiber  conduit 

Types  of  conduit 

Fiber* 

Iron 

Connecting  up  the  charging  circuit  of  storage  batteries. 

Connector,  buzzer 

Construction: 

Line  tools 

Of  manholes 

Tool  chest  and  contents 

Copper  vrire  (sec  Wire). 

Conts,  Signal  Corps,  standard  for  all  apparat  us 

Cross  arms,  dimensions 

Cross-connecting  wire - 


Current,  alternating 

Cycles 

Produced  in  telephony. 
Current: 

Direct 

Pulsating,  defined 


D. 

Data  relative  to  Kerite  compound 

Data  relative  to  Safety  compound 

Difference  of  potential 

Differential  telegraph  relay,  requirements 

Direct  current 

Distance  computed  by  means  of  sound 

Double  current  duplex  telegraphy 

Dry  batteries: 

Construction  of 

Internal  resistance  and  weights 

To  rejuvenate 

Used  with  various  apparatus 

Duplex  telegraphy '. 

Dynamometer  used  in  laying  and  recovering  submarine  cables. 


E. 

Edison  primary  battery,  type  V 

rOdison  storage  battery 

F'^Ieclrifal  ensnuecr's  tool  chest  and  contents 

F'jlcctrical instrument  case,  contents 

Elect  rical  instrument  case  and  contents 

Electric  drills  and  f)ther  special  tools 

Electrolysis  and  remedy 

Electromagnetism 

Electrostatic  capacity  measurements 

F'^Iectrostatic  induction 

Elenieiit.s  of  dnjilex  )elegrai)]iy 

I'^leinenls  of  j)olar  duplex  telegraphy 
Ivjuipment  issued  by  the  Signal  <'o 
ni<!ration... 

See  Chap.  8 


by  the  Signal  ('orps,  alphabetically  arranged  enu 
p.  I,  Tor  ulphabetical  list  or  all  Signal  Corps  apparatus  and 


52 

14 
18 


8 
supplies. 


(522) 


Subject  Index. 


13 


Subjects. 


Chap- 
ter 
No. 


Chap- 
ter 

page 
No. 


Exploring  roil: 

To  identify  cable-s  in  trench. . . 

To  locale  a  ground 

Extension  bells: 

How  to  connect 

Loud  ringing  and  indoor  type. 


Factory  tests: 

Of' cable 

Sample  of  record 

Faultfinder 

Fence-post  lines  for  aerial  construction 

Fiber  conduit 

Field  buzzer,  theory 

Field  equipment: 

Maintenance  of 

Miscellaneous 

Field  glasses,  description  of  each  type  supplied  by  the  Signal  Corps.. 

Field-induction  telegraph,  its  u.se 

Field  operations: 

Instruments  for  lines  of  information 

Selection  of  instruments 

Wire  used,  description 

Wire  used  in  emergencies 

Field  transportation 

Field  wire 

To  splice 

Fisher  cable  testing  set  No.  2,  description 

Fixture  Avire 

Formulae: 

For  converting  statute  miles  to  nautical  miles 

For  logarithmic  law  for  reducing  insulation  resistance  to  60°  F. . . 

For  mixing  concrete 

For  reducing  copper  resistance  to  60°  F 

For  testing  cables  for  breaks  and  grounds,  not  metallic  circuit. . . 

For  testing  cables,  for  breaks,  grounds,  and  earth  overlap 

For  testing  cables  for  breaks,  Jordan  and  Schonau's  modification. 

Matthiessen's,  for  soft  copper  wire 

Miscellaneous,  relative  to  vnres 

Reducing  resistance  to  a  given  temperature 

Specific  conducti\'ity 

Specific  resistance 

Specific  resistance  at  various  temperatures 

To  compute  distance  by  means  of  sound 

To  compute  value  of  insulation  when  testing  with  a  voltmeter. . . 

To  determine  capacity  of  circular  tank 

To  determine  number  of  sheathing  (armor)  ^vires  required 

L'sed  in  locating  faults  in  cable 

Used  in  locating  faults,  Prof.  Kennelly's  method . 

Front  Royal,  Va.,  remount  depot: 

Aerial  line  construction  employed 

Post  telephone  system 

Fuller  battery  cell 

Effect  of  age *. 

Fuses;  furnish  sample  if  other  than  standard  desired 

Standard 


11 


9 

4 

4 

4 

11 

11 

11 

9 

9 

9 

9 

9 

9 

9 

10 

9 

9 

11 

11 

5 
6 
1 
1 


19 

18 

22 
22 


6.=) 
70 
25 
31 
4.3 
27 

13 

87 
40 


28 
28 
27 
28 
26 
85 
85 
42 
83 

39 
68 
12 
59 
70 
64 
71 
32 
38 
32 
30 
30 
31 
39 

39 
34 
58 
59 

29 
25 
9 
10 
42 
42 


See  Chap.  8,  p.  1,  for  alphabetical  list  of  all  Signal  Corps  apparatus  and  supplies. 


46581°— 17 34 


(523) 


14 


Subject  Index. 


Subjects. 


G. 


Galvanized  iron  wire 

Characteristics 

Galvanometers,  reflecting: 

Ayrton  universal  shunt  used 

D"  Arson  val 

Do 

Remarks  on  shunts 

Shunts 

Sullivan 

Thompson 

Gauges,  wire 

Comparison  of  various  types 

Commonly  used 

Law  of  the  Brown  &  Sharpe  gauge 

General  data  concerning  the  storage  battery 

General  information,  lines  of  information i . . 

Lines  of  information  classified 

General  Order,  War  Department,  relative  to  post  telephone  systems. 

Glas.ses,  field,  types,  description,  etc. 

Gravity  battery  cell 

Internal  resistance  and  voltage 

Ground  for  signaling  over  long  submarine  cables 

Ground  rods 

Gyite-. 


H. 


Hammers,  marking 

Handholes,  for  underground  cable  systems 

Hand  reel 

And  wire  carrier,  how  used 

Hard-drawn  copper  wire 

Characteristics 

Heat  coils: 

And  protectors.  Western  Electric  and  Cook . 

For  switchboard  protectors 

House  wire 


Tdontifiration  of  cable  conductors 

Impurities  in  storage  battery  electrolyte 

Induction  coil 

Induction: 

Electromagnetic 

Electrostatic 

Magnetic 

Mutual  and  self-defined 

Induction  telegraph  set 

Duplex  operation 

Instructions  for  operating 

It«  use 

Theory 

To  u.se  as  a  closed-circuit  telegraph  set. 
Initial  charge  of  storage  batteries: 

Chloride  accumulator 

(iouid 

<  )f  various  makes 

Willard 


11 

11 

4 

11 

11 

11 

11 

9 

9 

9 

9 

1 

9 

9 

(i 

8 

1 

1 

11 


See  Chap.  8,  p.  1,  for  alphabetical  list  of  all  Signal  Corps  apparatus  and  supplies. 


(524) 


Subject  Index. 


15 


Subjects. 


Chap- 
ter 
No. 


Chap- 
tor 


Inside  twistcnl  pair  wire 

Inside  twi.sted  triple  conductor  wire 

In.=!pection,  maintenance 

In.spector's  pocket  tool  kit  and  contents 

Installation  of  cable: 

Aerial  cable 

(leneral 

Submarine  cable 

Submarine  cable,  precautions  to  avoid  rupture. 

I'nderground  cable 

Instrument  case,  electrical,  contents 

Instruments  for  field  lines: 

The  camp  telephone,  its  use 

The  buzzer,  its  use 

The  field  induction  telegraph,  its  use 

Instruments,  selection  of.  for  u.se  in  the  field 

Instrument  wagon,  how  ii.sed 

Insulatine 

Insulating  and  splicing  materials 

Insulating  compounds 

Insulation  measurements: 

Explanation  of  principle  involved 

To  determine  galvanometer  constant 

Insulation  test 

To  compute  values 

With  telephone  receiver 

Iron  conduit 


Junction  box,  target  range. . 


K. 
Keys: 

Employed  in  telegraphy 

Strap." 

Kit,  tool,  in.spector's  pocket,  and  contents. 
Knife  switches 


L. 

Lance  poles,  and  insulators 

Lance  trtick,  how  used 

Law  of  magnetic  induction 

Law  of  Brown  &  Sharpe  gauge 

Lead  sleeves  for  cable  splices 

To  determine  size 

Lightning  arresters: 

For  protecting  telephones 

Mason 

Moisture-proof  tA-pe 

Principle  of  operation 

Protective  feature 

Telegraph 

Line  construction.     (See  Aerial  line  construction.) 

Lines  of  force  defined 

Lines  of  information 

Classified 

Selection  of  instruments 

Liquid  conductors,  resistance  of 


10 


See  Chap.  8,  p.  1,  for  alphabetical  list  of  ail  Signal  Corps  apparatus  and  supplies. 


(525) 


16 


Subject  Index. 


Subjects. 


Chap- 
ter 
No. 


Local  batteiy  telei^hono: 

Desk  8et 

Garford,  and  circuits 

Garford  circuits 

Sumter  and  circuits 

Transmission 

Typical  circuit  traced 

Locat  ion  of  storage  battery 

Location  of  faults  in  telegraph  lines 

Logarithmic  law,  variations  of  insulation  resistance  with  temperature 
changes 


M. 


Magnetic  force 3 

Magnetic  induction 3 

Governing  laws 3 

Magnet,  to  construct 3 

Magnetism 3 

Electro 3 

Polarity  of  a  magnet 3 

Magneto,  telephone 3 

Action  explained , 3 

Automatic  circuit  opener 3 

Sizes  furnished  by  the  Signal  Corps 3 

Magneto  telephone  switchboards: 

15-line  size G 

50-line  size |  6 

50-line  size,  rewire  ringing  power  key 6 

Cordless  type 6 

To  stop  magneto  handle  unscrewing 6 

Maintenance: 

Inspection  of  post  telephone  systems 10 

Of  common  battery  telephones,  faults  likely  to  occur 6 

Of  dry  l)atteries. .'. • 10 

( )f  local  battery  telephones,  faults  likely  to  occur 6 

Of  motor  generators.     {See  "Motor  generators.  ") 

Of  post  telephone  systems 6 

( )f  power  switchboards 10 

Of  telephone  switchboards,  faults  likely  to  occur 6 

( )f  various  field  e(|uipment 10 

Storage-battery  reports 10 

Tools  for  the  purpose 10 

Manholes: 

Construction  of 4 

Formula  for  mixing  concrete 4 

[•"or  underground  conduit  system 4 

Mclliod  of  mixing  concrete 4 

Support  for  boiler-plate  cover 7 

Manner  of  listing  amounts  of  various  tyi)es  of  wire 8 

Marking  hammers 8 

Materials: 

f nsidating  and  splicing ." 8 

biiH-  ron.struct  ion 8 

MaltiiicsHcn's  standard  of  conductivity 9 

Mattliiessen  's  formula  for  soft  copper  wire 9 

Measurements: 

Capacity 4 

Insulation 4 

Mecliiinic 'h  tool  chest,  and  contisnts 8 

Megaphones,  (iber,  18-inch 8 

Sec  Chap.  8,  p.  1,  Tor  alphabetical  list  or  all  Signal  Corps  apparatus  and  supplies. 

(526) 


Subject  Index. 


17 


.Siibjpots. 


Megger,  tests  with 

Messenger  strand  (see  Aerial  line  construetion  ),  properties  of . 

Meter,  watt-hour,  installed  in  connection  with   common  battery 

telephone  systems 

^^etaI  terminal  boxes 

I !)  1 5  model 

Miscellaneous: 

Field  equipment 

Tests 


post 


Wires 

Miles-  to  convert  statute  miles  to  nautical  miles. 

Mogul  paint 

Moldings,  three  tj'pes  of 

^^onthly  storage-batterj^  report 

Morse  telegraphy.     (^S'ee  Telegraphy,  Aforse.) 
Motor  generator: 

Brushes 

Care  of  commutator 

Cause  of  overheating  of — 

Bearings 

Commutator : 

Cause  of  sparking 

Excessive  field  heating 

Maintenance  of 

Maintenance,  bearings 

Starting 

Stopping 

Throwing  or  leaking  of  oil 

Murray  and  Varley  loop  tests - 

Mutual  and  self-iuduction  defined 


O. 

OfTice  equipment,  telegraph  offices 

Office  wire 

Ohm  defined 

Ohms  law 

Applied  to  alternating  current 

Applied  to  a  part  of  a  circuit 

Applied  to  circuit  containing  ball  cry 

Ohmmeter: 

Description 

Directions  for  tising 

Location  of  faults  in  multiple  conductor  cable 

Model  1 904 -. 

Open-circuit  batteries 

Service  used  for 

Open-circuit  telegraph  system 

Operation  of  buzzer  defined 

<  )peration  oi'  telephone  transmitter 

Operation  of  long  submarine  c-ables  (See  Cables,  submarine,  long). 

( )utside  distributing  wire,  copper  clad 

Outside  twisted  pair  wire 

Overcharge  of  storage  batteries 

Ozite,  tluee  grades 


Pack  chests,  how  used. 

Paint,  Mogul 

Paraffiiic 


10 

8 

t; 
8 

8 

8 
9 
8 
9 
8 
8 
10 


10 
10 

10 
10 
10 
10 
10 
10 
10 
10 
10 
9 
3 


Chap- 
ter 

page 
No. 


See  Chap.  8,  p.  1,  for  alphabetical  list  of  all  Signal  Corps  apparatus  and  supplies. 


(r.27) 


18 


Subject  Index. 


Subjects. 


Chap- 
ter 
No. 


Chap- 
ter 

page 
No. 


Perforators,  transmitter  tape 11 

Photography 8 

Pigtail  and  clamp  insulators 

Pikes,  wire 

Pilot  cell  of  storage  battery 

Pipe  fitter's  tool  chest  and  contents 

Placing  storage  batteries  in  service  after  being  out  of  service 

Placing  storage  batteries  out  of  service 

Points  for  cable  testers 

Polar  duplex  telegraphy: 

Balancing 

Operation , 

Polar  relay 

Polarity  of  a  magnet 

Pole  changer,  for  polar  duplex  telegraphy 

Poles: 

Telegi^aph  and  telephone  {See  also  Aerial  line  construction") — 

Ceclar,  dimension  and  weights 

Steel  and  iron 

Tripod : 

Wooden,  dimensions 

Lance,  and  insulators 

Portable  anemometer  for  small-arms  target  ranges 

Portable  voltameter  issued  by  the  Signal  Corps 

Post  telephone  system: 

Care  of 

Common  battery  power  equipment 

Arrangement  of 

Battery  feed  where  battery  is  remote  from  switchboard 

Bridge  battery  feed  with  condenser .■ . 

Current  consumed  chargeable  to  Signal  Corps 

Leads  from  electric  lighting  main 

Motor  generator  and  mercury  arc  rectifier 

One  battery  only  to  be  installed  when  charged  by  a  generator. 

Power  switchboards 

Two  batteries,  when  charged  through  lamps 

WTiere  charging  current  is  alternating 

AMiere  watt-hour  meter  is  installed 

Common  battery  switchboards — 

Battery  voltage 

Connections  to  commercial  telephone  exchange 

Connections  to  protectors 

Description  of 

Lamp  line  and  lamp  supervisory  signals,  type 

Multiple  type 

Principal  circuits  of  all  above  200-line  size 

Principal  circuits  of  lamp  line  and  lamp  supervisory  signals 

type 

Sizes 

Type  now  furnished  in  the  50,  100,  and  L'OO  line  size 

Types  defined 

Visual  line  and  lamp  supervisory  si^'iials 

Visual  line;  and  visual  supervisory  signals 

Connections  to  telephones  remote  from  posts 

General  order  relative  to  post  telephone  systems 

(ieneral 

I  list  allat  ion  of  telephone  switchboard 

I.iglitning  arresters  for  telephones 

Lightning  arnater,  protective  features 

Local  liiitterv 

See  Chap.  8,  p.  1,  for  alphabelical  list  uf  all  Signal  Corps  apparatus  and  supplies. 


10 

4 

6 

35 

6 

36 

6 

35 

6 

36 

6 

39 

6 

39 

6 

38 

6 

37 

6 

39 

6 

38 

6 

38 

6 

39 

6 

6 

6 

18 

6 

33 

6 

9 

6 

16 

6 

16 

C 

17 

() 

19 

6 

9 

0 

16 

G 

6 

15 

6 

o 

I 

1 

26 

2 

3 

() 

21 

(528) 


Subject  Index. 


19 


Subjects. 


Post  telephone  system — Continued. 

Local  battery  (magneto)  switchboards.     {See  Switchboard.) 

Location  of  switchboards 

Maintenance 

Comnion  battery  installations,  faults  likely  to  occur 

Dry  batteries 

Inspections 

Local  battery  instruments,  faults  likely  to  occur 

Motor  generators.     (See  "Motor  generators. ") 

Power  switchboards 

Telephone  switchboards,  faults  likely  to  occur 

Tests 

With  megger 

\\'ith  post  testing  voltmeter 

Mason  lightning  arrester 

Moisture  proof  type  protector  (lightning  arrester) 

Monthly  storage  battery  report 

Never  ' '  boil  out "  rubber-covered  wire 

Operation  of  common  battery  switchboards — 

Switchboard,  200-line  size,  night  bell 

Switchboard,  night  bell 

Use  of  the  generator  call  drops 

\'isual  line  and  ^■isual  supervisory  signals 

Principle  of  operation  of  lightning  arrester 

Procedure  in  ''laying  out"  a  system 

Records — 

Cable  lengths,  slack  cable,  and  splices 

Component  parts  of  a  record 

General 

Location  of  duct  lines  and  trenched  cable 

Location  of  manholes 

Miscellaneous 

Necessary  Signal  Corps  forms  enumerated 

Post  telephone  connections  and  other  data 

Record  all  modifications 

Routing  of  cables  and  aerial  lines  and  location  of  structures. 

Show  ing  arrangement  of  power  equipment 

Special  circuits 

Terminals,  cross  connections,  and  spare  pairs  and  circuits... 
Requisitions  for  maintenance  supplies.     (See  "Requisitions.") 

Ringing  (calling )  apparatus 

Semiannual  inspection 

Switchboard  cable — 

Color  scheme ' 

Installation  of 

Use  of 

Switchboards — 

Cable  forms 

Connecting  up 

Construction  of 

To  expel  moisture 

Where  a  temporary  construction  form  can  not  be  used . . 

Locations 

Location  of  condensers 

Protector  apparatus,  general 

Protector  frames  and  protectors 

Protector  heat  coils 

Relative  to  unpacking 

To  test  connecting  cords 

Tools  for  maintenance  purposes 

See  Chap.  8,  p.  1,  for  alphabetical  list  of  all  Signal  Corps  apparatus  and 


Chap- 
ter 

No. 


Chap- 
ter 


0 

C 

G 
10 
10 

G 

10 

G 

10 
10 
10 

G 

G 
10 

G 

6 
6 
6 
6 
6 
6 

6 
6 
6 
10 
6 
6 
6 
6 
6 
6 
6 
6 
6 

G 
10 

6 
6 
6 

6 
6 
G 
G 
G 
6 
6 
G 
6 
6 
6 
6 
10 

supplies. 


(529) 


20 


Subject  Index. 


Subjects. 


Chai>- 
ter 
No. 


Chap- 
ter 


Post  telephone  system — Continued. 

Western  Electric  and  Cook  heat  coils  and  protectors 

Where  one  room  only  is  available  for  central  station  equipment . 

Post  testing  voltmeter 

Post  tool  chest  and  contents 

Potential  difference 

Potheads: 

For  paper  insulation  cable 

Directions  for  setting  up 

Filling  pothead  with  compound 

To  determine  dimensions  of  lead  sleeves 

For  rubber  insulation  cable 

Pothead  wire 

Power  cables 

Usually  in  Signal  Corps  stock 

Power  for  operating  telegraph  systems 

Power  required  for  initial  charge  of  storage  batteries 

Power  switchboards 

^laintenance  of 

Preparing  electrolyte  for  storage  batteries 

Primary  batteries 

Properties  of  strand 

Pulling  cable  in  conduits 

Fa-stening  rope  to  cable 

Pulsating  currents  defined 

Pinposes  for  which  storage  batteries  are  supplied 


R. 

Racking  cables  in  manholes 

Racks  for  storage  batteries,  construction  of 

Receiver,  telephone 

Recorder,  siphon 

Adjustment  of 

Auxiliary  apparatus 

Care  of 

Hybrid  type 

Motor .• 

Motor  operated  by  electric  light  current 

Miurhead  vibrator 

Recording  cable  lengths  installed 

Records  of  a  post  telephone  system: 

Arrangement  of  power  equipment 

Cable  length,  slack  cable,  and  splices 

Component  parts 

General 

Location  of  manholes 

Miscellaneous 

Post  telephone  connections  and  other  data 

Record  all  modifications 

Routing  of  ca})le  and  aerial  lines  and  location  of  structures. 

Signal  ( 'orps  forma  enumerated 

Special  circuits 

Tenninals,  cross  connections,  spare  pairs,  and  circuits 

Records  of  a  small  anna  target  range  signaling  system 

Component  parta  listed 

How  prepared 

Oflicesfnrnibhed 

Signal  Corps  forma  used 

Upkeep  of 


6 

6 

10 


10 
1 
1 

8 
4 
4 
1 
1 


4 

1 

3 

11 

11 

11 

11 

11 

11 

11 

11 

4 

6 
6 
6 
6 
6 
6 
6 
C 
G 
6 
6 
6 
7 
7 
7 
7 
7 
7 


See  Chap.  8,  p.  1,  for  alphabetical  list  of  all  Signal  Corps  apparatus  and  supplies. 


(530) 


Subject  Index. 


21 


Subjects. 


Keels,  cable: 

Collect  a  quantity  before  returning  them 

Return  lagging  with  reels 

To  be  numbered 

Transfer  of  cable  from  one  reel  to  another 

Reels,  hand 

Reflecting  galvanometer: 

A>Tton  universal  shunt 

D'Arsohval 

Do.. 

Remarks  on  shunt 

Shunts 

Sullivan 

Thompson 

Regular  charge  of  storage  battery 

Regulations  concerning  requisitions  .     (See  " Requisitions.") 

Relay,  polar,  for  Morse  telegraph 

Relays,  telegraph 

Repeaters,  telegraph 

Mlliken 

Weiny 

Closed  circuit  repeating  open  circuit  signals  and  vice  versa 

Requisitions: 

Department  signal  officers,  regulations  concerning 

For  maintenance  supplies 

From  State  militia  organizations 

Items,  regulations  concerning 

Property  officers,  regulations  concerning 

Sample  items 

Do!;!!!;;;!!!!;;!!!;_;!!!!!!!!!!!;;;!!;;;;j;;;^^;;^^;;!^!^! 

Signal  Corps  field  companies,  regulations  concerning 

Those  who  prepare  them,  regulations  concerning 

To  be  serially  numbered 

With  some  items  necessarv  to  show  either  manufacturer  or  size,  or 

both " 

Reserve  tj^e  of  dry  cells 

Internal  resistance  and  weights 

Testing 

To  rejuvenate 

To  place  in  service 

Resistance: 

Of  conductors 

Of  liquid  conductors 

Specific 

Specific  and  relative  conductivity  of  conductors 

Units  of 

Ringer,  telephone 

Operation 

Resistance  of  windings 

Rings,  bridle 

Rods,  ground,  types 

Rubber  covered  wire 


4 
4 
4 
4 

8 

11 
11 

4 
11 
11 
11 
11 

1 


10 
10 
10 
10 
10 
10 
10 
10 
10 
10 
10 

10 

1 
1 
1 

1 
1 

1 

9 
9 
9 
9 
3 
3 
3 
8 
8 
8 


S. 


Screw,  anchor 

Secondary  batteries.     (See  Batteries,  storage.) 
Ser\-ice  buzzer.     [See  Buzzer.) 

Service  testing  battery  for  cable  testing 

Service  tool  hag;  and  contents 


43 

G8 


See  Chap.  8,  p.  1,  for  alphabetical  list  of  all  Signal  Corps  apparatus  and  supplies. 


(531) 


09 


Subject  Index. 


Subjects. 


Chap- 
ter 


Set.  induction,  telegraph 

Instructions  for  operating 

Duplex  operation 

Theory 

To  use  as  a  closed -circuit  telegraph  set 

Shunt  and  key  for  cable  testing 

Signal  cart 

Equipment 

Signal  Corps: 

Blank  forms,  reference 

Specifications  enumerated 

Standard  cords  for  all  apparatus 

Single  current  or  Steams  duplex  telegraphy. . . 
Siphon  recorder 

Adjustment 

Auxiliary  apparatus 

Care  of 

Hybrid  type 

T>arge  and  Small 

Motor > 

^lotor  operated  by  electric-light  current. . . 

Muirhead  vibrator 

Sleeves,  lead: 

To  determine  size  for  cable  splicing 

Various  sizes,  for  cable  splicing 

Small  arms  target  ranges.  (See  Target  range.) 
Solder 


"Wiping,  used  in  cable  splicing 

Soimders,  telegraph - . 

Adju.=!tment  of 

Special  tools 

Specifications,  Signal  Corps,  enumerated 

Specific  and  relative  resistance  and  relative  conductivity  of  conductors. 

S])ecific  resistance 

Speech,  transmission  of,  telephonically 

Splicing  and  insulating  materials 

Splicing  cables.     (See  Cable  splicing.) 

Spring  hammers  and  other  special  tools 

Storage  battery.     (See  Batteries,  storage.) 

Storage  liattery  report,  monthly 

Strand ,  properties  of 

Strap  keys 

Strip,  standard  porcelain 

Submarine  cable.     (See  Cable,  submarine.) 
Sul)terranean  cable.     (See  Cable,  subterranean.) 
S^^^t<■hlx)ard: 

Power 

Maintenance  of 

Telegraph 

And  repair  parts 

Terminal  and  battery  arrangement 

Teleplioiie,  r<'la1ive  to — 

"  Boiling  out "  rublx;r-covered  wire 

Cable,  color  scheme 

Cable  forms 

Connecting  uj) 

Construction  of 

A\  hen!  temporary  const  ruction  form  can  notlx'  uh<'<I 


10 


See  Chap.  8,  p.  1,  fur  alphabetical  list  of  all  Signal  Curp.s  apparatus  and  supplies. 


(r..rj) 


Subject  Index. 


23 


Subjects. 


Chap- 
ter 
No. 


Chap- 
ter 

page 
No. 


Switchboard — Continued . 

Telephone,  relative  to — Continued. 

Cable,  installation  of , 

tlse  of 

To  expel  moisture  froia  cable 

Camp,  description  of 

Common  buttery,  and  repair  parts 

Description 

Connection  to  commercial  exchange 

Connections  to  protectors 

T.amp  line  and  lamp  supersdsory  signal  type. 

Multiple  t^'pe 

Operation  of  night  bell 

Power  equipment 

Arrangement  of 

Battery  feed  when  battery  is  remote  from  switchboard 

Bridge  battery  feed  with  condenst^r 

Current  consumed  chargeable  to  Signal  Corps; 

Leads  from  electric  lighting  mains 

Motor  generator  and  mercurj^  arc  rectifiers 

One  batterv^only  when  charged  by  a  generator 

Power  switchboards 

Two  batteries  when  charged  through  lamps 

When  watt-hour  meter  is  installed 

Where  charging  ciu'rent  is  alternating 

Principal  circuits  of  lamp  line  and  lamp  supervisory  signal 

type 

Sizes 

Tvpes,  defined 

200-line  size— 

Night  bell , 

Principal  circuits  of  sizes  above 

Use  of  generator  call  drop 

Visual  line  and  lamp  supervisor}'  signals 

Now  furnished  in  50,  100,  and  200  line  boards 

Visual  line  and  ^isual  supervisory  signals 

Operation  of - .  j 

Voltage  used | 

Installation  of I 

Local  battery  (magneto),  and  repair  parts ^ | 

Connections  to  protectors * 

Cordless  type 

15-line  size 

50-line  size 

50-line  size,  rewire  ringing  power  key 

To  prevent  magneto  handle  from  unscrewing 

Location — 

General 

Specific ' 

Of  condensers 

Protective  apparatus,  general 

Protector  frame  and  protectors 

Heat  coils 

Testing  connecting  cords 

L'npacking 

Ringing  apjiaratiis '. . 

Western  Electric  and  Cook  heat  coils  and  protectors 

Where  one  room  only  is  available  for  central  station  eqidpment 
Switches,  knife 


See  Chap.  8.  p.  1.  for  alphabetical  list  of  all  Signal  Corps  apparatus  and  supplies. 


(533) 


24 


Subject  Index. 


Subjects. 


Chap- 
ter 
No. 


Chap- 
ter 


Tables: 

Alaskan  cable  data 11 

Amounts  of  sag  of  messenger  strand 5 

Amounts  of  sag  of  aerial  wires  at  various  temperatures 5 

Approved  types  of  double  lead-covered,  paper  insulation  subter- 
ranean cable 4 

Approved  types  of  paper  insulation — 

Submarine  cable '4 

Subterranean  cable 4 

Approved  types  of  rubber  insulation — 

Submarine  cable 4 

Subterranean  cable 4 

Cable- 
Paper  insulation — 
Armored — 

.    Detailed  characteristics  of  all  types 8 

Weights  and  lengths S 

Lead  covered,  unarmored — 

Lengths  and  reels , S 

Detailed  characteristics  of  all  t j-pes S 

Cable  power — 

Usually  in  stock  at  supply  depots 4 

Special  types  that  have  been  purchased 8 

Rubber  insulation,  submarine — 

Detailed  characteristics  of  all  types 8 

Lengths ". 8 

Weights 8 

Subterranean — 

Detailed  characteristics  of  all  types 8 

Lengths jl 8 

Weights 8 

Color  scheme  of  switchboard  cable G 

Commercial  value  of  copper  strands 9 

Commercial  value  of  hard  drawn  copper  wii'e 9 

Comparison  of  various  wire  gauges 9 

Conductors  and  insulation,  temperature  coefficients 9 

Conversion,  statute  miles,  nautical  miles,  kilometers 4 

Copper  wire — 

Carrying  capacities  for  int(>rior  wiring 9 

Feet  per  ohm  at  various  temperatures 4 

Strands,  carrying  capacity  for  interior  wiring 9 

Ohmic  resistance — 

32°  F. ,  59°  F. ,  G8°  F 4 

77°  F.,  122°  F.,  167°  F 4 

Resistance  per  pound,  various  sizes 4 

Data  pertaining  to  Seattle-Si tka  caltle  when  laid 11 

Depth  to  set  aerial  line  poles  in-  ground 5 

Desired  dimension  of  wooden  poles 5 

Do 8 

Dimensions  and  weights  of  cedar  poles 8 

Do 8 

Dimension  of  standard  cross  arms 5 

Do 8 

Dimension,  weight,  and  length  of  ])ure  c()|>]K'r  wire 4 

Faetora  for  logaritliinic  law  for  rc(hi(iiig  compounds  to  ()((°  F 4 

Gal  vani/.ed -iron  wire,  circular  mils,  area,  weight,  resistance,  break- 
ing strength,  lengths 8 

Ilarfl-drawn   c()p|)er  wire,    weight,   resistance,  tensile  etrengtli, 

lengths 8  I         8  1 

See  Chap.  8,  p.  1,  for  alphabetical  UnI  o(  all  Signal  Corps  apparatus  and  supplies. 


(534) 


Subject  Index. 


25 


Subjects. 


Chap- 
ter 
No. 


Cliap- 

ter 
page 

No. 


lablos — Continued. 

Internal  resistance  of  various  typ>e8  of  batteries f) 

Lead  sleeves  for  cable  splicing I  4 

Logarlt hmic  law,  temperature  coeflicients i  4 

Mils  diameter  of  sizes  in  B.  &  S. ,  and  B.  W.  G .  gauges i  8 

Miscellaneous  in  format  ion 9 

Number  and  location  of  submarine  cables  installed 9 

Nimaber  of  cable  pairs  required  for  battery  feed,  common  battery  ! 

telephone  systems 6 

Power  cable  usually  in  stock  at  supply  depots 4 

Properties  of  mcsenger  st rand 8 

Properties  of  various  sizes  of  messenger  strand o 

Ratings  of  chloride  accumulators 1 

Resistance  of  li(juid  conductors 9 

Resistance  of  pure  copper  wire  at  75°  F 4 

Sizes  and  ratings  of  storage  batteries 1 

Specific  and  relative  resistance  and  relative  conductivity  of  con- 
ductors   9 

Temperature  coefficients — 

For  copper,  difference  in  degrees 11 

Of  various  metals .* 9 

Okonite,  Halurshaw,  Safety  and  Bishop  compounds 4 

Standard  Underground  rubber  "  D  "  and  Kerite 4 

To  reduce  copper  to  60°  F 4 

Tensile  strength  of  copper  wire 9 

Units  of  resistance 9 

Weights  and  resistance  of  18  per  cent  German  silver  wire 8 

Tagging  cables  in  manholes. 4 

Tank,  circular,  to  determine  capacity 9 

Target  range  signaling  systems: 

Buzzer  and  buzzer-annunciator  systems 7 

,Care  of 10 

Classes  defined 7 

Distribution  boxes 7 

General 7 

.Installation  of  outlet  boxes,  types  2  and  3  systems 

Latest  installation  of  buzzer  and  strap  keys 

Location  of  annunciator,  master  switch,  and  distributing  box 7 

Location  of  outlet  boxes 7 

Maintenance  inspection 10 

Maintenance  of  dry  batteries 10 

Maintenance  test 10 

Manhole  cover  support 

Manhole  Tisually  used 

Master  switches 

Military  drills  on  range 

Original  installation  of  buzzer  and  strap  key 

Portable  anemometer 

Protect  cable  from  rodents 7 

Push  button  and  outlet  boxes 7 

Range  officer's  station - 

Requisitions  for  maintenance  supplies.     {See  "  Requisitions.") 
Records — 

Component  parts  listed 7 

How  prepared 7 

Location  of  duct  line  and  trenched  cable 10 

Offices  furnished 

Required 

Signal  Corps  forms  used 

Upkeep  of 

See  Chap.  8,  p.  1,  for  alphabetical  list  of  all  Signal  Corps  apparatus  and  supplies. 

(535) 


26 


Subject  Index. 


Subjects. 


-Continued. 


Target  range  .signaling  system- 
Semiannual  inspection 10 

Separate  and  d  iminishing  cable? 7 

Source  of  power  for  operating  buzzor  and  buzzer-annunciator 

systems 7 

Target  range  junction  box 7 

Through  circuits 7 

Tools  for  maintenance  purposes 10 

Type  1  range,  telephone  box - . .  7 

Tj'pea  defined - 7 

Use  of  can  terminal 7 

Use  of  sewer  flush  pipes 7 

WTien  range  is  telephonically  connected  to  post  telephone  system  .  7 

Wiring  at  butts 7 

Technical  equipment  issued  by  the  Signal  Corps,  alphabetically  ar- 
ranged enumeration 8 

Telegraph  induction  set 2 

Duplex  operation 2 

Instructions  for  operating 2 

Theory  of 2 

To  use  as  a  closed-circuit  telegraph  set 2 

Telegraph  lines: 

Blavier  test  for  location  of  leaks ! . .  9 

Common  faults  encountered 9 

Effect  of  poor  ground  connection 9 

Instniments  for  locating  faults 9 

Location  of  faults 9 

To  determine  nature  of  fault  and  approximately  locate 9 

To  increase  the  working  value.-. 9 

Telegraph  switchboards  and  repair  parts 8 

Telegraphy,  Morse 2 

Adjustment — 

Feeling  for  a  distant  station : 2 

For  maximiun  strength 2 

Of  apparatus I  2 

Of  sounders !  2 

Closed  circuit  system 2 

Duplex — 

Artificial  line 2 

Balancing  the  polar  duplex 2 

Battery  type 2 

Bridge  type 2 

Differential  relay,  requirements 2 

Double  current 2 

Essential  elements 2 

Polar- 
Essential  elements 2 

Operation  of 2 

The  pole  changer 2 

Single  current ,  or  Steams 2 

Telegraphy 2 

The  polar  relay 2 

Transmitter 2 

W.  U .  pole  changer 2 

Keys  employed 2 

Lightning  arresters 2 

Office  equipment 2 

Office  Hwil  ch 2 

On  short  submarine  cables 2 

Open  circuit  system 2 

See  Chap.  8,  p.  1,  for  alphabetical  list  of  all  Signal  Corps  apparatus  and  supplies. 

(530) 


trr 
page 
No. 


Subject  Index. 


27 


Subjects. 


Telegraphy,  Morse — Continued. 

Over  submarine  rabies.     {See  Cables,  submarine.) 

Power  for  operating  system 

Relays 

Repeaters 

Closed  circuit  repeating  open  circuit  signals  and  vice  versa. 

Milliken 

Test  for  operation 

Weiny 

Weiny ,  operation  described 

Sounders 

Switchboards 

Terminal  switchboard  and  battery  arrangement .' 

Wet-weather  effects 

Telephones: 

Cable  testing 

Camp 

And  repair  parts  for 

Battery  employed 

First  and  later  models,  to  di.stingui,<^h 

Hand-set 

Hook  switch 

How  constructed 

Its  use 

Do.. 

Screw  driver  with  each  instrument 

Common  batterj' — 

And  repair  parts  for 

Dean,  Wheatstone  bridge  circuit  described 

General 

Desk 

Common  batterj- — 

Garford  circuits 

North  Electric  circtuts 

Local  batter}^ 

Garford  circuits 

Field,  and  repair  parts  for 

Local  battery — 

And  repair  parts  for 

Typical  circuit  t  raced 

Switchboard  location 

Theory  of 

Types  of  instruments 

Various  types  and  repair  parts  for 

Wall 


Common  battery — 

Circuits  traced 

North  Electric  circuits 

Siunter  circuits 

Western  Electric  circuits 

Local  batten.'^ 

Garford  circuits 

Sumter  circuits 

Telephone  ."switchboards.     (See  Switchboards,  telephone.) 
Telephone  systems.     (See  Post  telephone  systems.) 
Telephony : 

Common  battery  operation  explained 

Common  battery  transmission 

See  Chap.  8,  p.  1,  for  alphabetical  list  of  all  Signal  Corps  apparatus  and 


2 

4 

2 

o 

2 

7 

2 

25 

4 

45 

3 

23 

8 

80 

3 

24 

3 

24 

3 

26 

3 

26 

3 

24 

3 

23 

9 

28 

3 

26 

8 

78 

G 

8 

3 

17 

3 

20 

3 

23 

3 

23 

3 

16 

3 

16 

8 

80 

8 

79 

3 

13 

6 

1 

3 

4 

3 

12 

8 

78 

3 

21 

3 

19 

3 

22 

3 

.   19 

3 

18 

3 

1 

3 

14 

3 

6 

3 

6 

supplies. 


(537) 


28 


Subject  Index. 


Subjects- 


page 

No. 


Telephony — Continued. 

Condenser  defined 

Difference  between  local  and  common  battery  transmission 

Electromagnetic  induction 

Electromagnetism 

Electrostatic  induction 

How  articulate  speech  is  transmitted 

Laws  of  magnetic  induction 

Local  battery  transmission 

Lines  of  force  defined 

Magnetic  force 

Magnetic  induction 

Magnetism 

Operation  explained 

Automatic  circuit  opener 

Sizes  furnished  by  the  Signal  Corps 

Receiver 

Ringer 

Operation 

Resistance  of  windings 

The  induction  coil 

The  magneto 

Theory  of 

The  transformer 

To  make  a  magnet 

Transmitter 

Telephone 

Telescopes,  description  of  each  type  supplied  by  the  Signal  Corps. . . 

Temperature  coefficient , 

Conductor  and  insulation 

Of  various  metals 

Temperature  effects  on  storage  batteries 

Terminal  boxes: 

First  metal  ones 

General 

Metal,  terminal  strips  used 

Metal,  1915  model 

Terminal  strips,  standard 

Terminals,  for  cable,  fused  and  unfused 

Tests,  cable: 

After  cables  installed,  duties  of  tester 

After  installation  and  being  spliced 

After  installation,  correction  for  leads  to  instruments 

Blavier,  for  locating  leaks  and  grounds 

Cable-t4?sting  telephone 

Capacity  measurements  when  cable  exceeds  100  miles  in  length. 

ComV)ined  shunt  and  key 

CondenwT,  standard 

Cond uctor  resisfance 

Conversion  table,  statute  miles,  nautical  miles,  kilometers 

Copper  wire — 

Feet  yxjr  ohm  at  various  temperatures 

Ohmic  re.sistance — 

32°  F.,50°  F.,  68°F 

77°  F.,  122°  F.,  167°  F 

Ohms  per  pound — 

32*"  F.,  59°  F.,  68°  F 

77°  F.,  122°  F.,  167°  F 

See  Chap.  8,  p.  1,  for  alphabetical  list  of  all  Signal  Corps  apparatus  and 


supplies. 


(538) 


Subject  Index. 


29 


Subjects. 


Tests,  cable — Continued. 

Data  relative  to  oompouiul — 

Kerite 

Safety 

Dimensioji,  weight,  and  length  of  piire  copper  wire 

Electrical  instrument  case,  contents 

Electrolysis,  to  detect 

Electrostatic   capacity 

Factor  used  to  change  statute  miles  to  nautical  miles 

Factory  tests 

Sample  of  record 

Do 

Fisher  cable  testing  set,  No.  2 — 

Description  of , 

Measuring  capacity  wath 

Measuring  conductor  resistance  with 

Measiuing  insulation  with 

Murray  loop  test  with 

Special  Wheatstone  bridge  used  with 

Varley  loop  test  with 

Formula  for  reducing  copper  resistance  to  60°  F 

Identification  of  conductors 

Insulation — 

Measurements,  author's  explanation  of  principle  involved . . 

Resistance 

To  compute  values 

To  determine  galvanometer  constant 

With  telephone  receiver 

LocatioTi  of — 

Break  in  conductor,  using  improvised  apparatus 

Cross  by  means  of  the  voltmeter 

Fault  with  ohmeter,  in  multiple  conductor  cable 

Ground — 

HaAing  a  high  resistance,  with  improvised  apparatus 

Single  conductor  cable,  with  improvised  apparatus. ... 

With  exploring  coil 

With  improvised  apparatus , 

All  conductors  grounded , 

Conductor  grounded  at  two  places 

Explanation  of  principle 

Logarithmic  law — 

Factors  for  reducing  compounds  to  60°  F , 

P'or  reducing  insulation  resistance  to  60°  F.,  formula 

Temperature  coefficients , 

Variation  of  insulation  resistance  with  temperature  change. . 
Long  submarine  cables.     (See  '"Cables,  submarine,  long.'') 

Method  of  making  testing  after  installation 

Murray  and  Varley  loop  tests 

Notes  on  capacity  measurements 

Ohmeter,  model  1904 

Ohmic  resistance — 

Comparison  of  ohmeter  with  WTieatstone  bridge 

Directions  for  using  ohmeter 

With  voltmeter  and  ammeter 

One  hundred  thousand  ohm  box,  standard 

Points  for  the  cable  tester 

Recommended  treatises  on  tests 

Record  readings  obtained  on  leads 

Reflecting  D'Arsonval  galvanometer 


4 
4 
4 
4 
4 
4 
4 
4 
4 
4 

11 
11 
11 
11 
11 
11 
11 
4 
4 

4 
4 
4 
4 
9 

9 
9 
9 

9 
9 
9 
9 
9 
9 
9 

4 

4 
4 
4 

4 

9 

11 

4 

4 
4 
9 
4 
-1 
11 
4 
4 


See  Chap.  8,  p.  1,  for  alphabetical  list  of  all  Signal  Corps  apparatus  and  supplies. 


46581°— 17 


-35 


(539) 


30 


Subject  Index. 


Subjects. 


Chap- 
ter 


^l 


Tests,  cable — Continued. 

Resistance  of  pure  copper  wire  at  75°  F 

Service  testing  battery 

Special  instruments  used 

Specimen  of  record 

Standard  cable  constants 

Temperature  coefficients — 

Kerite  and  Standard  Underground  Co. 's  rubber  '"  D  " 

Okonite,  Habirshaw,  Safety,  and  Bishop  compounds 

The  double  scale  voltmeter 

The  faultfinder 

To  eliminate  earth  current  effects 

To  identify  cable  in  trench  by  means  of  an  exploring  coil 

To  measure  length  of  single  conductor  cable 

To  reduce  copper  to  60°  F 

Voltammeter,  portable,  issued  by  the  Signal  Corps 

With  improvised  apparatus 

With  post-testing  voltmeter , 

With  the  megger 

With  WTieatstone  bridge — 

Graphical  demonstration 

Post-office  form  of  instrument 

Precautions  in  operating 

Principle  of  instrimient  explained 

Simplest  measurement 

Tests,  miscellaneous: 

For  operation  of  telegraph  repeaters 

Instruments  for  locating  faults  in  telegraph  lines 

Location  of  crosses  or  leaks  in  telegraph  Lines  with  the  wire  bridge . 

Location  of  faults  in  telegraph  lines 

Of  electrolyte  for  storage  batteries 

Ohmic  resistance  of  telegraph  line — 

Practical  connections 

With  voltmeter  and  ammeter 

To  approximately  locate  faults  in  telegraph  linos 

With  voltammeter — 

To  measure  internal  resistance  of  a  battery 

W'ith  voltmeter — 

Difference  of  potential 

Resistance  of  3,000  to  250,000  ohms 

Resistance  less  than  3,000  ohms 

Resistance,  using  a  known  resistance 

To  measure  ciu-rent 

To  measure  internal  resistance  of  a  battery 

Voltage  of  a  number  of  cells  of  a  battery,  connected  in  series. . 
With  Wheatstone  bridge,  to  measure  resistance  of  telegraph  line. . . 

Toggle  bolts 

Tool  chests: 

Aeroplane,  and  contents 

Cable  splicer's,  and  contents 

Construction,  and  contents 

Electrical  engineer's,  and  contents 

Mechanic's,  and  contents .^ 

Pipe  fitter's,  and  contents 

Post,  and  contents 

Tool  bag,  service,  and  contents 

Tool  kit,  inspector's  pocket,  and  contents 

Tools: 

For  maintenance  purposes 

Special 

Transfer  of  cable  from  one  reel  to  another 


4 
4 
11 
4 
4 

4 
4 
9 
9 

11 
9 

11 
4 
9 
9 

10 

10 

9 
9 
9 

9 
9 


See  Chap.  8,  p.  1,  for  alphabetical  list  of  all  Signal  Corps  apparatus  and  supplies. 

(540) 


Subject  Index. 


31 


Subjects. 


Chap- 
ter 


Transformer,  principle  of 

Transmitter: 

Automatic,  for  use  on  long  submarine  cables 

Duplex  telegraphy 

Tape  perforators 

Telephone 

Telephone,  operation 

Transportation  in  the  field 

Treatment  of  storage  batteries  when  they  are  to  stand  idle. 

Tripod  aerial  line  construction 

Trucks,  lance,  how  used 

Tungsten  type  A  battery 

Internal  resistance  and  weight 

Type  numbers  for  cable,  system  of  assigning 

Types  of  conduit  for  underground  cable  systems 

Types  of  telephones 


U. 


Underground  installation  of  cable: 

Conduit  construction 

Procedure 

Trenching 

Two  methods 

Units  of  resistance 


V. 

\'arley  and  Murray  loop  tests 

Voltaic  cell 

Voltammeter,  portable,  issued  by  the  Signal  Corps. 
^'oltmeter: 

Post  testing 

To  locate  a  cross 

''Volt  drops,"  defined 

Volt  defined 


9 
1 
9 

10 
9 
1 
1 


W. 

"Wagon,  instrument,  how  used 

Watt-hour  meter,  installed  in  connection  with  post  telephone  systems. . 

Weatherproof  wire '. 

Weiuey  telegraph  repeaters 

Operation  described 

Wheatstone  bridge: 

Graphical  demonstration 

Post-otfice  form  of  instrument 

Precautions  in  operating 

Principle  explained 

Simplest  measurement 

Used  at  Alaskan  cable  offices 

Wire  (sec  also  Tables,  tests,  etc.): 

Aluminum,  carrj-ing  capacities 

And  insulation ,  temperature  coefficients 

Bridle. 

Buzzer 

Copper — 

Carrying  capacities  for  interior  wiring 

Hard  dra\\ni — 

Advantages  for  line  construction 

Commercial  values 0  ! 

See  Chap.  8,  p.  1,  for  alphabetical  list  of  all  Signal  Corps  apparatus  and  supplies. 


9 
9 
9 
c 

9 
11 

9 
9 


(541^ 


32 


Subject  Index, 


Subjects. 


Chap- 
ter 
No. 


Chap- 
ter 

page 
No. 


Wire — Continued . 

Copper — Continued . 

Soft,  Matthiessen 's  formula 

Strands — • 

Carrying  capacities  for  interior  wiring 

Commercial  standards 

Tensile  strength 

Cross  connecting 

Designate  size  in  mils 

Field 

To  splice 

Fixture 

P'or  all  purposes,  enumeration 

For  radio  telegraph  installations 

Galvanized  iron 

Characteristics 

Hard-drawn  copper 

Characteristics 

House 

Inside  twisted  pair 

Inside  twisted  triple  conductor 

Lengths  and  resistance  of  18  per  cent  German  silver. 

Manner  of  listing  amounts  of  various  types 

Miscellaneous 

Office 

Outside  distributing,  copper  clad 

Outside  twisted  pair 

Pot  head 

Relative  to  manufacture , 

Rubber-covered 

Used  in  field  operations — 

Description 

In  emergencies 

Useful  constants  and  formulae 

Weatherproof 

Wire  carrier 

Wire  carrier  and  hand  reel,  how  used 

Wire  carts,  description  and  how  used 

Type  "  L, "  extra  and  maintenance  parts 

Wire  gauges 

Commonly  used 

Comparison  of  various  types 

Law  of  the  Brown  &  Sharpe  gauge 

Wire  pike 

Wooden  poles,  dimensions 


32 


9 

36 

9 

35 

9 

34 

8 

83 

8 

81 

8 

85 

8 

85 

8 

83 

8 

82 

8 

82 

8 

85 

8 

85 

8 

84 

8 

84 

8 

83 

8 

82 

8 

82 

8 

87 

8 

86 

8 

86 

8 

86 

8 

84 

8 

84 

8 

83 

8 

81 

8 

83 

9 

27 

9 

28 

9 

38 

8 

84 

8 

87 

9 

27 

9 

26 

8 

33 

9 

32 

9 

33 

9 

33 

9 

33 

8 

89 

8 

49 

Sec  Chap.  8,  p.  1,  for  alphabetical  list  of  all  Signal  Corps  apparatus  and  supplies. 


(542) 


ILLUSTRATION  INDEX. 


niustmtioDs. 


No. 


Aerial  line  construction: 

Arrangement  of  tackle 

Attaching  brackets  to  poles 

Cable  box    

Changing  direction  of  messenger 

Deadman  and  anchor  rod 

Double  arming  poles 

Fence  post  lines 

Gale  crossing 

Guard  wires    

Guying— 

Across  road 

At  comers 

At  curves 

At  road  crossings 

Installation  effused  can  terminal 

Line  transposition 

Long  Spans — 

Construction  of  saddles 

Methods  of  terminating 

Additional     

Messenger  strand — 

Deadending 

Guying 

Supports 

Through  bolt  type 

Method  of  guying  to  rock 

Pole  brace 

Pole  steps    

Preparation  of  poles 

Shims  and  clamps 

Splicing  messenger  strand 

Terminal — 

Can — 

Fused    

Unfused    

Pole 

Unfused — 

Installed 

Installation  of 

Test  station 

Tripod  lines 

Over  ice 

Tying  hard-drawn  copper  wire  to  insulators 
Tying  and  splicing  iron  and  steel  wires  .  . 
Wires  on  insulators 

Corner  pole 

Alaskan  tripod  lines 

Over  ice 

Anchors,  screw,  composition 

Arresters,  lightning,  telephone 

Moisture-proof  type 


5-27 
5-- 3 
5-4 
5-28 
5-10 
5-2 
5-34 
5-35 
5-14 

5-13 
5-7 
5-9 
5-8 
5-29 
5-19 

5-39 
5-38 
5-40 

5-21 
5-22 
5-25 
5-26 
5-11 
5-12 
5-6 
5-1 
5-23 
5-24 


5-30 
5-31 
5-5 

5-33 
5-32 
5-20 
5-36 
5-37 
5-17 
5-18 
5-15 
5-16 
5-36 
5-37 
8-25 
6-1 
6-2 


P.L. 
P.L. 


P.L 
P.L. 


(543) 


83 


34 


Illustration  Index. 


No. 


Illustrations. 


C^ 


B. 

Bag,  tool,  service 

Battery  cells  connected: 

In  multiple 

In  series 

Battery  cells: 

Edison  primary  type  V 

Fuller    .' 

Gravity      

Battery  dry  cells,  standard  sizes 

Battery  reserve  dry  cells,  standard  sizes 

Battery: 

Service,  testing,  used  in  cable  testing 

Storage — ■ 

Assembly  of  parts 

Do 

Do 

Do 

Do 

Do 

Charging  for  telegraph  systems 

Oiloride 

Gould    

Stand  for 

Do 

Willard     

1  cell,  for  relays  and  sounders  of  telegraph  systems  .  . 

Bell,  extension,  loud  ringing 

Blavier  test,  location  of  grounds 

Bridge,  Wheatstone: 

Graphical  demonstration 

Post-office  form 

Bridle  rings,  enamel  coaled 

Box: 

Cable .  . 

Metal,  terminal,  1915  model 

100,000  ohm,  standard,  used  in  cable  testing 

Buzzers  connected  to  a  telegraph  line 

Buzzer,  connector,  type  A 

Buzzer: 

Field,  simplified  circuit 

With  interrupter 

With  transmitter    

With  transmitter  and  interrupter 

Service 

Circuits     

Dismantled 

Sending  and  receiving  Morse  signals,  circuits  employed 


8--21 

1--8 
1-7 

1--6 
1-5 
1--4 
1--2 
1--3 

4--34 

1-A 
1--B 
1-C 

1--D 
1--E 
1--F 
2--25 
1--10 
1-12 
1-13 
1-14 
1-11 
2-26 
8-3 
9-31 

9-20 
9-19 
8-24 

5-4 
8-1 
4-31 
3-29 
8-29 

3-25 
3-26 
3-27 
3-28 
3-31 
3-30 
3-32 
3-33 


68 

13 
13 

11 
9 
8 
5 
6 

43 

20 
20 
20 
20 
20 
20 
30 
22 
24 
26 
27 
23 
30 
23 
24 

15 
14 
72 

9 
21 
41 
29 


P.L. 
P.L. 
P.L. 


P.L 


P.L 


P.L 


Cable: 

Box     

Grips,  improvised  and  manufactured 
Long  submarine,  switchboard  used  . 

Power 

Pulling,  position  of  reel 

Racking  in  manholes 

Reel,  with  lagging 


5-4 
4-15 
11-1 
4-5 

4.-14 

4-16 
4-6 


(644) 


Illustration  Index. 


35 


Illustrations. 


No. 


.S 


Cable — Continued. 
Splicing — 

Paper  insulation  cable 

Do  

Do  

Do  

Do  

Do  

Do  

Do  

Do  

Do  

Construction  of  pothead 

Rubber  insulation,  submarine 

Sleeve  used  in  splicing  type  251  cable 

Submarine — 

Paper  insulation 

Rubber  insulation 

Subterranean — 

Paper  insulation 

Rubber  insulation 

System — 

Conduit  ends 

Connecting  underground  to  aerial  cable 

Diagrammatic 

Distribution     

Manhole 

Removable  forms 

With  concrete  top 

Testing  {Also  see  Tests) — 

Capacity 

Coefficients  for  reducing  insulation  resistance  to  60°  F 

Copper  resistance — 

Murray  and  Varley  loop,  simplified  diagram 

Connections     

Curve  sheets  for  Jona  and  other  graphs 

D'Arsonval  reflecting  galvanometer,  wall  type 

Electrostatic  capacity,  simplified  diagram 

Fisher  cable  testing  set,  No.  2 

Arrangement  of  apparatus 

Connections     

Wheatstone  bridge  arrangement 

Galvanometer  constant 

Insulation     

Insulation  resistance,  simplified  diagram 

Jordan  and  Schonau's  modification  of  earth  overlap  test,  diagram  of  connections 
Location  of  grounds 

Clark's  potential  tests- 
Connections     

Connections  at  distant  station 

Earth  overlap  test,  diagrammatic 

Prof.  Kennelly's  method,  copper  resistance  connections 

Simple  loop  test,  connections 

Ohmeler,  theory  of 

Plan  of  testing  table,  Seattle  cable  office 

Resistance  measurement  with  ohmeter 

Shunt,  Ayrlon,  universal 

Connections     


4--18 
4--19 
4--20 
4--21 
4-22 
4--23 
4--24 
4--25 
4-26 
4-27 
4--28 
4--17 
4--29 


4-- 4 
4-- 3 


4-40 
4-43 

1-34 
1-26 
1-42 
1-21 
1-32 
1-28 
1-30 
1-31 
1-29 
4-38 
4-39 
1-33 
1-43 


1-39 

1-40 
1-41 
1-38 
1-37 
4-41 
1-35 
4-42 
1-23 
1-24 


4-2     3 
4-1      2 


4-8 
4-13 
4-7 
4-12  15 
4-9  12 
4-11  14 
4-10    13 


(545) 


36 


Illustration  Index. 


Illustrations. 


Cable — Continued. 
Testing — Continued. 

Shunt,  simplified  diagram 

Special  instruments  used 

Telephone     

Circuits     

Test  room  connections,  U.  S.  A.  T.  Bumside  .... 

Thompson  reflecting  galvanometer 

Wheatstone  bridge,  for  measuring  conductor  resistance 
Camp  telephone: 

And  circuits 

Dismantled 

Switchboard     

Can,  terminal,  fused 

Installation  of 

Unfused     

Unfused,  installed 

Unfused,  installation  of 

Carrier,   wire 

Cart,  signal 

Case: 

Electrical  instrument 

Reagent     

Cells,  battery: 

Connected  in  multiple 

Connected  in  series 

Dry- 
Standard  sizes    

Reserve,  standard  sizes 

Edison  primary,  type  V 

Fuller    

Gravity     

Chests,  tool: 

Cable  splicer's 

Construction     

Eleclrical  engineer's 

Mechanic's,  No.  2 

Pipe  fitter's 

Post •     


Closed  circuit  telegraph  system 

Coefficients  for  reducing  insulation  resistance  lo  60°  F 

Condenser,  standard,  used  in  cable  testing 

Connector,  buzzer,  type  A 

Cook  protector,  details 

Cords,  standard: 

Field  equipment 

Switchboard — 

Connecting 

Transmitter  and  receiver 

Telephone,  post  and  Artillery  type 

Terminals  for 

Conduit  ends 


D'Arsonvai  reflecting  galvanometer,  wall  type 

Distributing  frame 

Duplex  telegraphy.    (See  Telegraphy.) 
Dynamolor,  ringing 


No. 


1--8 
1--7 


1- 

.     1- 
.    1- 

:■   1- 
1- 


-2 
-3 

-6 
-5 
-4 

8--18 
8--17 
8--16 
8--15 
8--19 
8--20 
2--1 
4-43 
4-33 
8-29 
6-- 8 


8-- 6 

37 

8-- 5 

36 

8-- 7 

38 

8-- 9 

40 

4-- 8 

11 

11--21 

32 

6-- 3 

5 

6--38 


-.a 
5;= 

..ft 


P.L 


P.L 
P.L 
P.L 
P.L 

P.L 


P.L 


42 


P.L 
P.L 
P.L 


P.L 


(546) 


Illustration  Index. 


37 


Illastrations. 


No. 


&  "3  2 


E. 


Electricalinslniment  case 

Exploring  coil,  test  to  locate  ground 
Extension  bell,  loud  ringing  .... 


F. 


8--14 
9--24 
8-- 3 


9--32 


Faultfinder 

Fence  post  lines: 

Aerial  lines 

Gate  crossing 

Field  buzzers: 

Connected  to  a  telegraph  line  . 

Simplified  circuits 3-25 

With  interrupter 3--26 

With  transmitter 

With  transmitter  and  interrupter 

Frame,  distributing 

Front  Royal  Remount  Depot: 

Cordless  switchboard     

Circuits     

Open     

Fuses,  standard  types 


G. 


Galvanometers: 

Connections  for — 

Capacity 4-40 

Insulation     4-39 

Obtaining  constant 4-38 

D'Arsonval,  reflecting,  wall  type 11-21 

Reflecting,  D'Arsonval  type 4-30 

Thompson,  reflecting 11-20 


5-34 
5-35 

3-29 


3-27 
3-28 
6-3 

6-24 
6-26 
6-25 
8-10 


H. 


Hand  receiver,  telephone 


3-8 


Hand  reel    8-28 


I. 


Induction  telegraph  set 

Circuits     

Theory  of  operation 

Inspector's  pocket  tool  kit 

Instrument  case,  electrical 

Instruments,  special,  used  in  testing  cable 


Key  and  shuni  used  in  cable  testing 

Key,  strap,  large 

Key,  telegraph.    ( See  Telegraph. ) 
Kit,  tool,  inspector's  pocket  .... 


Lightning  arrester,  telephone 

Moisture-proof  type 

Lioe  construction.    ( See  Aerial  line  constniclion.) 


2-27 
2-29 
2-28 
8-22 
8-14 
11-25 


4-32 
8-11 

8-22 


6-1 
6-2 


P.L 


P.L 


P.L 


f.L 


P.L 
P.L 


(547) 


38 


Illustration  Index. 


Illustrations. 


Ohmeter: 

Model  1904 

Resistance  measurement 

Test,  to  locate  grounds 

Theory  of 

Ohms,  100,000,  standard,  used  in  cable  testing 
Open  circuit  telegraph  system 


Fike,  wire    

Plug  switch  and  lightning  arrester,  telegraph 

Portable  voltammeler 

Post  testing  voitmeler 

Polhead  for  paper  insulation  cable 

Power  cable     

Protector  cabinets,  for  telephone  switchboards 
Protectors: 

Cook,  details 

Western  Electric,  details 


R. 


Reagent  case  

Receiver,  hand,  telephone 

Record  of  telephone  system.    (See  Telephone  systems,  record. ) 

Rectifier,  mercury  arc 

Reel: 

Cable,  with  lagging 

Hand 

Reflecting  galvanometer,  D'Arsonval  type 


No. 


Line  construction  material 

Messenger  supports 

Long  spans  in  aerial  lines: 

Construction  of  saddles 

Method  of  terminating 

Method  of  terminating,  additional 

Long  submarine-cable  testing.  {See  Cable  testing  and  tests.) 
Long  submarine-cable  telegraphy.    {See  Telegraphy.) 

M. 

Magneto  generator,  telephone 

Theory  of 

Voltage  curve 

Manholes: 

For  cable  system 

Removable  forms 

With  concrete  top 

Material,  line  construction 

Messenger  supports 

Megger     

Mercury  arc  rectifier 

Morse  telegraphy.   (See  Telegraphy  and  telegraph  systems.) 

Motor  generator 

Molding,  standard  types 


i^i=; 


8-12 
8-13 

5-39 
5-38 
5-40 


3-7 
3-  5 
3"  6 

4-9 
4-11 
4-10 
8-12 
8-13 
10-1 
6-35 

6-34 
8-23 


4-35 

4-42 
9-22 
4-41 
4-31 
2-2 


8-30 
2-11 
9-21 
10-2 
4-28 
4-5 
6-7 

6-8 
6-9 


1-9 
3-8 

6-35 

4-6 

8-28 
4-30 


40 


P.L. 
P.L. 

P.L. 


(548) 


Illustration  Index. 


39 


Illustrations. 


Relay: 

Box,  telegraph     

Telegraph,  main  line 

Ringer,  telephone 

Ringing  dynamotor     

Rings,  bridle,  enamel  coated 

Repeater,  telegraph: 

Circuits  for  0.  C.  and  C.  C.  operation 

Milliken,  theory  of 

Weiny,  theory  of 


No. 


zr 
«  s 


S. 

Screw  anchor,  composition     

Service  buzzer     

Circuits     

Dismantled 

Sending  and  receiving  Morse  signals,  circuits  employed  .  . 

Service  testing  battery  used  in  cable  testing 

Shunt  and  key  used  in  cable  testing 

Shunt,  Ayrton,  universal 

Connections      

Shunt  used  in  cable  testing,  simplified  diagram 

Signal  cart 

Sleeve  used  in  splicing  type  251  cable 

Small  arms  target  range  signaling  systems.    (See  Target  Range.) 
Sounder,  telegraph: 

Mainline 

4-ohm 

Splicing  cable.    (See  Cable  splicing.) 
Standard  cords.    (See  Cords,  standard.) 

Standard  type  of  fuses 

Storage  battery: 

Assembly  of  parts 

Do 

Do 

Do 

Do 

Do 

Chloride    

Gould     

Stand  for 

Do 

Willard 

Strap  key,  large 


Strip,  terminal,  standard 

Submarine  cable.    (See  Cable,  submarine.) 
Subterranean  cable.    (See  Cable,  subterranenan.) 
Switchboard: 

Cable.    (See  Switchboard,  telephone,  forming  cable  conductors.) 

Camp  telephone 

Telegraph  — 

Intermediate 

Power  connections 

Terminal  type 

Telephone — 

Common  battery,  50-line  visual 

Distributing  frame 


2-7 
2-- 6 
3--10 
6--38 
8-24 

2-16 
2-14 
2~1S 


8-25 
3-31 
3--30 
3-32 
3-33 
4-34 
4-32 
11-23 
11-24 
11-22 
8-4 
4-29 


2-8 
2-9 


8-10 

1-A 
1-B 
1-C 
1-D 
1-E 
1-F 
1-10 
1-12 
1-13. 
1-14 
1-11 
8-11 
8-2 


2-10 
2-13 
2-12 


8-26    77 

5 
8 

7 


6-6 
6-3 


(549) 


40 


Illustration  Index. 


Illustrations. 


No. 


Switchboard — Continued. 
Telephone — Continued. 

Forming  cable  conductors 

Do 

Do 

Do 

Do 

Lamp  line  and  lamp  supervisory  signals — 

Circuits     

Inoperation 

Principal  circuits 

Test  circuits 

Local  battery  type,  cordless 

Circuits     

Open     

Local  battery  type — 

15  line 

15  line,  circuits 

50  line 

50  line,  circuits 

Locking  relays,  circuits 

Power  type  No.  1 

Power  type  No.  4 

Protector   cabinet 

Visual,  circuits 

Visual  line  signal,  lamp  supervisory  cord  circuit 

Visual  night  bell  circuit 

50-100  line,  and  protector  cabinet 

200  line  night  bell  circuit 

200-line,  generator  drop  circuit 

Switchboard  used  with  long  submarine  cable 

System,  cable.   (See  Cable  system.) 


6-28 
6-27 
6-29 
6-30 
6-31 

6-15 
6-17 
6-19 
6-16 
6-24 
6-26 
6-25 

6-20 
6-21 
6-22 
6-23 
6-18 
6-36 
6-37 
6-7 
6-10 
6-14 
6-11 
6-32 
6-12 
6-13 
11-1 


29 
28 
29 
30 
31 

16 
17 
19 
17 
25 
26 
26 

20 
21 
23 
24 
18 
40 
41 
11 
13 
15 
13 
34 
14 
14 
5 


P.L. 


Target  range: 

Outlet  box,  round  pattern 

Outlet  box,  1915  model 

Pushbutton 

Type  No.  1  system 

Outlet  box 

Telephone    box 

Type  No.  2  system — - 

Using  diminishing  cable 

Using  separate  cables  to  butts  .  .  . 

Type  No.  3  system 

Types  Nos.  2  and  3  systems — 

Distributing  box 

Installation  of  strap  key  and  buzzer 

Manhole 

Master  switch 

Outlet  box,  installation  of 

Through  circuits 

Target  range  junction  box  ...  . 

Use  of  can  terminal 

Telegraph  induction  set 

Circuits 

Theory  of  operation 


7-- 2 
7-3 
7-1 
7-4 
7-5 
7-6 

7-7 
7-8 
7-9 

7-14 
7-15 
7-12 
7-11 
7-10 
7-16 
7-13 
7-17 
2-27 
2-29 
2-28 


P.L 


(660) 


Illustration  Index. 


41 


No. 


Illustrations. 


Telegraph  systems: 

Closed  circuit 

Key,  closed  circuit — 

Legless  type    

Leg  type 

Key,  open  circuit,  leg  type 

Main  line  sounder 

Opencircuit 

Plug  switch  and  lightning  arrester 

Relay- 
Box    

Mainline 

Repeater  - 

Circuits  for  0.  C.  and  C.  C.  operation 

Milliken,  theory  of 

Weiny,  theory  of 

Switchboard — 

Intermediate    

Power,  connections    

Terminal  type 

4-ohm  sounder 

Telegraphy,  duplex: 

Battery,  duplex 

Bridge,  theoretical  connections 

Polar,  circuits 

Polarized  relay,  theoretical  connections 

Pole  changer 

Single  current — 

Theoretical  connections 

Do 

Do 

Telegraphy  over  submarine  cables: 

Actual  connections  at  Alaskan  cable  offices 

Current  supply  at  Seattle  terminus  of  Seattle-Sitka  cable 

Cuttriss  automatic  transmitter,  connections 

Double-current  telegraphy 

Key  used  by  the  Signal  Corps 

3-station  connections 

large  siphon  recorder 

Connections     

Morse  open  circuit  connections 

Polarized  relay  set,  connections 

Single  current,  open  circuit,  repeater  sets 

Simplified  diagram  of  connections 

Siphon  recorder    - 

Duplex  and  simplex  systems,  connections 

Muirhead's,  arrangement  of  circuit 

Siphon  recorder  set,  simplified  connections 

Siphon  recorder — 

Muirhead,  vibrator  circuits 

To  operate  motor  from  electric  lighting  circuit  .  .  . 

Small  siphon  recorder 

Telegraphy,  power: 

Charging  storage  battery 

Current  for  relay  and  sounders 

Telephone: 

Cable  testing 

Circuits 


2-1 

2-4 
2-3 

2-5 
2-8 
2-2 
2-11 

2-7 
2-6 

2-16 
2-14 
2-15 

2-10 
2-13 
2-12 
2-9 

2-22 
2-23 
2-21 
2-20 
2-24 

2-17 
2-18 
2-19 

11-17 
11-14 
11-19 
11-3 
11-5 
11-4 
11-9 
11-10 
11-2 
11-8 
11-6 
11-7 

11-18 
11-16 
11-15 

11-12 
11-13 
11-11 

2-25 
2-26 

4-36 
4-37 


7 
5 

22 
23 
20 
19 
25 

14 
15 
16 

25 
22 
27 

8 

9 

9 
17 
18 

7 

14 
11 
12 

26 
25 
24 

21 

22 
19 

30 
30 

45  P.L 
46 


(551) 


42 


Illustration  Index. 


No. 


Illustrations. 


SF= 


Telephone — Continued. 

Camp,  and  circuits 

Camp,  dismantled 

Circuits — 

Common  battery,  simplified 

Local  battery,  simplified      

Simplified — 

Using  four  telephone  receivers      •  . 

two  telephone  receivers  .  , 

Desk,  common  battery 

Garford  Manufacturing  Co.,  circuits  as  installed 

North  Electric  Co.,  circuits  as  installed 

Desk,  local  battery — 

Garford  Manufacturing  Co 

Sumter  Manufacturing  Co.,  circuits 

Hand  receiver 

Local  battery,  circuits 

Magneto-generator 

Theory  of 

Voltage  curve 

Power  switchboards.    (See  Switchboards,  telephone,  power.) 

Ringer 

Switchboards.   (See  Switchboards,  telephones.) 

Switchboard,  camp 

Systems — 

C.  B.,  motor  generator 

C.  B.,  power  equipment  in  switchboard  room 

C.  B.,  power  switchboard — 

Type  No.  1 

Type  No.  4 

C.  B.,  rectifier,  mercury  arc 

C.  B.,  simpHfied  diagram  of  circuits 

C.  B.,  visual  line  signal  operation 

Dynamotor,  ringing 

Record    - 

Arrangement  of  power  equipment 

Cable  splices  and  lengths 

Connections  and  cross-connections  of  cable  conductors 

Connections  and  other  data 

Location  of  manhole 

Routing  of  lines  and  location  of  structures 

Special  arrangement 

Special  circuits 

Transmitter 

Wall,  common  battery 

North  Electric  Co.,  circuits  as  installed 

Sumter  Manufacturing  Co.,  circuits 

Western  Electric  Co.,  circuits 

Wall,  local  battery 

Garford  Manufacturing  Co.,  circuits 

Sumter  Manufacturing  Co.,  and  circuits 

Terminal  box,  metal,  1915  model 

Terminal  can: 

Fused     

Installation  of 


23 
•24 

4 
3 

2 
1 

18 
22 
21 

15 
13 
■8 
11 
■7 
■5 
■6 

-10 

-26 

34 
33 

36 

•37 
35 
•4 
•5 
38 

43 
40 
41 
•45 
•42 
-39 
46 
44 
9 
-19 
20 
17 
16 

-14 
-12 
-1 

-30 
-29 


12 

77 

37 
36 

40 
41 
38 
7 
7 
42 

47 
45 
46 
49 
47 
44 
50 
48 
11 
21 
22 
19 
18 

16 
14 

21 

27 
26 


P.L 
P.l. 


P.L. 


P.L. 


P.L. 
P.L 


P.L. 


P.L 


P.L 
P.L 

P.L 


(052) 


Illustration  Index. 


43 


UlustrdtioDs. 


Terminal  can — Continued. 

Unfused    

Installed 

Installation  of 

Terminal  strip,  standard 

Tests: 

Blavier,  location  of  grounds 

Emergency  insulation 

Improvised  bridge — 

Location  of  crosses 

Location  of  grounds 

Location  of  faults — 
Murray  loop — 

Location  of  crosses 

Location  of  grounds 

The  faultfinder 

Varley  loop — 

Location  of  crosses 

Location  of  grounds 

With  exploring  coil,  location  of  grounds 

With  improvised  apparatus — 

All  conductors  faulty 

Do 

Conductor  parted 

Using  a  galvanometer 

Using  a  telephone  receiver 

With  ohmeter,  location  of  grounds 

Measuring  ohmic  resistance — 

By  means  of  voltmeter  and  milliammeter 

Of  telegraph  line  by  means  of  voltmeter  and  milliammeter 

Of  telegraph  line  by  means  of  voltmeter  and  milliammeter,  practical  connections 

Ohmic  resistance,  fall  of  potential 

Wheatstone  bridge - 

Circuits,  diagrammatic 

Conventional  diagrams 

Graphical  demonstration 

Post-office  form 

Principle  employed 

With  voltmeter — 

Difference  of  potential — 

At  extremities  of  a  coil 

Between  two  points  on  a  wire 

Location  of  crosses , 

To  measure  ohmic  resistance 

Using  a  known  resistance 

Voltage  of  a  battery 

Thompson  reflecting  galvanometer 

Tool  bag,  service 

Tool  chests: 

Cable  splicer's 

Construction     

Electrical  engineer's 

Mechanic's  No.  2 

Pipe  filler's 

Post 

Tool  kit,  inspector's  pocket 


No. 


til 


8- 


P.L 


(553) 


44 


Illustration  Index. 


Illustrations. 


No. 


6 

q 

;2; 

6 

f5 

?', 

c 

^ 

.c 

u 

'1 

SF! 


Transmitter,  telephone 

Tripod  lines 

Over  ice    .... 


Voltaic  cell 

Voltamineter,  portable  .  . 
Voltmeter: 

Post  testing 

Test,  to  locate  crosses 


W. 


Western  Electric  protector  . 
Wheatstone  bridge: 

Post-office  form  .... 

Graphical  demonstration 

Wirecarrier 

Wirepike 


3-- 9 
5-36 
5--37 


9--21 

10--  2 
9-23 


6-9 

9-19 
9-20 
8-27 
8-30 


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